Whole genome transcriptome analysis has revealed that a large proportion of the genome in higher metazoa is transcribed, yet only a small proportion of this transcription is protein-coding. One possible function of non-coding transcription is that it enables complex and diverse body plans to evolve through variation in deployment of a relatively common set of protein-coding genes. Functional studies suggest that long non-coding RNAs (lncRNAs) regulate gene expression via diverse mechanisms, operating in both cis and trans to activate or repress target genes. An emerging theme common to lncRNA function is interaction with proteins that modify chromatin and mediate epigenetic regulation. The Hox gene complexes are particularly rich in lncRNAs and require precise and fine-tuned expression to deploy Hox transcription factors throughout development. Here we identify and functionally characterize two novel lncRNAs within the D. melanogaster Hox complex, in the interval between Scr and Antp. We use nascent transcript fluorescent in-situ hybridization (ntFISH) to characterize the embryonic expression patterns of each lncRNA with respect to flanking Hox genes, and to analyze co-transcription within individual nuclei. We find that the transcription of one lncRNA, ncX, is an initial response to early transcription factors and may activate Scr expression, while transcription of the other lncRNA, ncPRE is consistent with activation and/or maintenance of Scr expression. ntFISH performed in D.virilis embryos revealed the presence of a lncRNA ortholog with highly similar expression to ncX, indicating functional conservation of lncRNA transcription across ~60 million years of evolution. We identify the ncPRE lncRNA locus as a binding site for multiple proteins associated with Polycomb/Trithorax response elements (PREs/TREs) and show that DNA encoding the ncPRE lncRNA functions as a bona fide PRE, mediating trans-interactions between chromosomes and silencing of nearby genes. We find that transcription through the ncPRE DNA relieves silencing, suggesting a role for endogenous transcription of the ncPRE lncRNA in relieving Polycomb-silencing and enabling Scr activation. We demonstrate that both lncRNA transcripts are required for proper Scr expression, and over-expression of either lncRNAs from ectopic genomic loci has no effect on Scr expression, but ectopic expression at the endogenous locus is associated with ectopic Scr activation, indicating that the lncRNA-mediated regulation functions locally at the site of transcription on the chromosome. ncX may mediate transvection effects previously observed at the Scr locus, independent of the protein Zeste. Together our results support a model of competing mechanisms in the regulation of Scr expression - a background of Polycomb repression acting from the ncPRE locus, which in the first thoracic segment is counteracted by lncRNA transcription and Trithorax binding to ncPRE, enabling activation and maintenance of Scr expression. This work provides a functional insight into the complex regulatory interactions between lncRNAs and epigenetic mechanisms, essential to establish and maintain the precise expression pattern of Hox genes through development.

Während der embryonalen Neurogenese spielt die Repression neuraler Gene in nicht neuralen Zellen, sowie in neuralen Vorläuferzellen durch den REST (repressor element silencing transcription factor)-Komplex eine wichtige Rolle. Durch die schrittweise Inaktivierung diese Komplexes im Verlauf der Differenzierung werden neurale Genexpressionsprogramme gesteuert. Zusätzlich kommt bei der Kontrolle der räumlichen und zeitlichen Regulation der Genexpression während der Neurogenese verschiedenen miRNAs eine wichtige Rolle zu. So konnte in vorangegangenen Arbeiten im Zebrafischen gezeigt werden, dass miR-26b die Transkription eines wichtigen Effektorproteins des REST-Komplexes, CTDSP2 (C-terminal domain small phosphatases), während der Neurogenese negativ reguliert. Da darüber hinaus die miR-26 Repression zu einer stark verminderten neuronalen Differenzierung führte, kommt diesem regulatorischen Schaltkreis eine zentrale Rolle bei der Neurogenese im Zebrafisch zu. Die zusammen mit ihren Ctdsp-Wirtsgenen koexprimierte miR-26 Familie liegt in Vertebraten evolutionär hoch konserviert vor. Analog zum Zebrafisch konnte im murinen in vitro ES-Zell Differenzierungssystem gezeigt werden, dass miR-26 die Expression von Ctdsp2 reprimiert. Weiterhin konnte in diesem System gezeigt werden, dass auch Rest ein miR-26 Zielgen ist und dass der Verlust der miR-26 zu einem Arrest der differenzierenden Zellen im neuronalen Vorläuferstadium führt. Zusammengenommen deuten diese vorangegangenen Arbeiten auf eine zentrale Rolle der miR-26 während der Neurogenese hin. Die hier vorgestellte Arbeit zielte zunächst darauf ab die Regulation des REST-Komplexes durch die miR-26 auf molekularer Ebene besser zu verstehen. Der Verlust der miR-26 Bindestelle in der Ctdsp2 mRNA führte zu einer erhöhten Ctdsp2 Expression, beeinflusste aber nicht die terminale Differenzierung zu Neuronen. Im Gegensatz hierzu führte der Verlust der miR-26 Bindestelle in der Rest mRNA zu einem Arrest der Differenzierung im neuralen Vorläuferzellstadium. Zellen in denen die miR-26 Bindestelle in Rest deletiert war, zeigten zudem, genau wie miR-26 knockout (KO) Zellen, eine erhöhte Expression von REST-Komplex Komponenten, sowie eine verringerte Expression von REST-regulierten miRNAs. Zusammengenommen weisen diese Daten daraufhin, dass während der Neurogenese im Säugersystem die Inaktivierung von Rest durch miR-26 für die Maturierung von Neuronen eine zentrale Rolle spielt. Ein weiterer Fokus dieser Arbeit lag auf der Regulation der miR-26 Expression während der Neurogenese. Vorangegangene Arbeiten in nicht-neuronalen Zelltypen identifizierten die lnc (long-non-coding) RNA Malat1 als eine ce (competitive endogenous) RNA der miR-26. Um den Einfluss von Malat1 auf die miR-26 Expression während der Neurogenese zu untersuchen, wurde zunächst mittels CRISPR/Cas9 der vollständige Malat1-Lokus in ESCs deletiert. Der Verlust von Malat1 führte zu einer erhöhten Expression der miR-26 Familienmitglieder sowie deren Ctdsp-Wirtsgene. Weiterhin war die Proliferation von Malat1 KO neuronalen Vorläuferzellen stark vermindert, was mit einer Erhöhung der Frequenz seneszenter Zellen einherging. Durch die Inaktivierung von miR-26 in differenzierenden Malat1 KO ESCs konnte dieser proliferative Phänotyp aufgehoben werden. Darüber hinaus konnte eine verstärkte neuronale Differenzierung dieser Zellen beobachtet werden. Zusammenfassend zeigen diese Daten, dass neben der Regulation des REST-Komplexes durch miR-26 auch die Kontrolle des Zellzyklus über die Malat1-vermittelte Regulation der miR-26 in neuronalen Vorläuferzellen einen kritischen Schritt bei der Differenzierung von neuronalen Vorläuferzellen zu maturen Neuronen darstellt. / During embryonic neurogenesis, repression of neural genes in non-neural cells, as well as in neural progenitor cells by the REST (repressor element silencing transcription factor) complex, plays an important role. The gradual inactivation of this complex during differentiation controls neural gene expression programs. In addition, different miRNAs play important roles in controlling the spatial and temporal regulation of gene expression during neurogenesis. For example, previous work in zebrafish demonstrated that miR-26b negatively regulates the transcription of a key effector protein of the REST complex, CTDSP2 (C-terminal domain small phosphatases), during neurogenesis. Since miR-26 repression also resulted in severely reduced neuronal differentiation, this regulatory circuit plays a central role in zebrafish neurogenesis. The miR-26 family, co-expressed with its Ctdsp host genes, is evolutionarily highly conserved in vertebrates. Analogous to zebrafish, miR-26 was shown to repress Ctdsp2 expression in a murine in vitro ESC differentiation system. Furthermore, in this system, it was shown that Rest is also a miR-26 target and that loss of miR-26 leads to arrest of differentiating cells at the neuronal progenitor stage. Taken together, these previous analyses suggest a central role for miR-26 during neurogenesis. The work presented here first aimed to better understand the regulation of the REST complex by miR-26 at the molecular level. Loss of the miR-26 binding site in Ctdsp2 mRNA increased Ctdsp2 expression but did not affect terminal differentiation into neurons. In contrast, loss of the miR-26 binding site in the Rest mRNA resulted in arrest of differentiation at the neural progenitor cell stage. Cells in which the miR-26 binding site was deleted in Rest also showed increased expression of REST complex components, as well as decreased expression of RESTregulated miRNAs, just like miR-26 knockout (KO) cells. Taken together, these data indicate that during mammalian neurogenesis, inactivation of REST by miR-26 plays a central role in the maturation of mammalian neurons. Another focus of this work was on the regulation of miR-26 expression during neurogenesis. Previous analyses in non-neuronal cell types identified the lnc(long-non-coding)RNA Malat1 as a ce(competitive endogenous)RNA of miR-26. To investigate the effect of Malat1 on miR-26 expression during neurogenesis, the complete Malat1 locus was deleted in ESCs using CRISPR/Cas9. Loss of Malat1 resulted in increased expression of miR-26 family members as well as their Ctdsp host genes. Furthermore, proliferation of Malat1 KO neural progenitor cells was greatly reduced, which was accompanied by an increase in the frequency of senescent cells. Inactivation of miR-26 in differentiating Malat1 KO ESCs abrogated this proliferative phenotype. In addition, increased neuronal differentiation of these cells was observed. In conclusion, these data demonstrate that in addition to regulation of the REST complex by miR-26, cell cycle control via Malat1-mediated regulation of miR-26 in neuronal progenitor cells is a critical step for the differentiation of neuronal progenitor cells into mature neurons.

During infection, bacteria need to adapt to a changing environment and have to endure various stress conditions. Small non-coding RNAs are considered as important regulators of bacterial gene expression and so allow quick adaptations by altering expression of specific target genes. Regulation of gene expression in the human-restricted pathogen Neisseria gonorrhoeae, the causative agent of the sexually transmitted disease gonorrhoea, is only poorly understood. The present study aims a better understanding of gene regulation in N. gonorrhoeae by studying small non-coding RNAs. The discovery of antisense RNAs for all opa genes led to the hypothesis of asRNA-mediated degradation of out-of-frame opa transcripts. Analysis of asRNA expression revealed a very low abundance of the transcripts and inclusion of another phase-variable gene in the study indicates that the asRNAs are not involved in degradation of out-of-frame transcripts. This doctoral thesis focuses on the analysis of trans-acting sRNAs. The sibling sRNAs NgncR_162 and NgncR_163 were discovered as post-transcriptional regulators altering expression of genes involved in metabolic processes, amino acid uptake and transcriptional regulation. A more detailed analysis by in silico and transcriptomic approaches showed that the sRNAs regulate a broad variety of genes coding for proteins of central metabolism, amino acid biosynthesis and degradation and several transport processes. Expression levels of the sibling sRNAs depend on the growth phase of the bacteria and on the growth medium. This indicates that NgncR_162 and NgncR_163 are involved in the adaptation of the gonococcal metabolism to specific growth conditions. This work further initiates characterisation of the sRNA NgncR_237. An in silico analysis showed details on sequence conservation and a possible secondary structure. A combination of in silico target prediction and differential RNA sequencing resulted in the identification of several target genes involved in type IV pilus biogenesis and DNA recombination. However, it was not successful to find induction conditions for sRNA expression. Interestingly, a possible sibling sRNA could be identified that shares the target interaction sequence with NgncR_237 and could therefore target the same mRNAs. In conclusion, this thesis provides further insights in gene regulation by non-coding RNAs in N. gonorrhoeae by analysing two pairs of sibling sRNAs modulating bacterial metabolism or possibly type IV pilus biogenesis. / Bakterien müssen sich während des Infektionsprozesses an eine sich veränderte Umgebung anpassen und sind dabei zahlreichen Stressfaktoren ausgesetzt. Kleine, nicht-kodierende RNAs gelten als wichtige Regulatoren der bakteriellen Genexpression und ermöglichen daher eine schnelle Anpassung durch eine Veränderung der Expression spezifischer Ziel-Gene. Die Regulation der Genexpression des Humanpathogens Neisseria gonorrhoeae, Auslöser der Geschlechtskrankheit Gonorrhö, ist bis jetzt kaum verstanden. Die vorliegende Studie soll durch die Analyse kleiner, nicht-kodierender RNAs zum besseren Verständnis der Genregulation in Gonokokken beitragen. Durch die Entdeckung von antisense-RNAs für alle opa Gene wurde die Hypothese entwickelt, dass diese für den Abbau von opa Transkripten außerhalb des Leserahmens verantwortlich sind. Eine Analyse der asRNA Expression zeigte jedoch, dass diese sehr wenig exprimiert werden und auch die Untersuchung eines anderen phasenvariablen Gens weist darauf hin, dass die asRNAs keine Bedeutung für den Abbau von Transkripten außerhalb des Leserahmens haben. Der Schwerpunkt der Doktorarbeit liegt auf der Untersuchung trans-codierter sRNAs. Die Zwillings-sRNAs NgncR_162 und NgncR_163 agieren als post-transkriptionelle Regulatoren, die die Expression von Genen verändern, die bei Stoffwechselprozessen, Aminosäureaufnahme und transkriptioneller Regulation eine Rolle spielen. Eine detailliertere Analyse durch in silico- und Transkriptom-Studien zeigte, dass die sRNAs ein großes Spektrum an Genen regulieren, die für Proteine des Zentralstoffwechsels, der Aminosäurebiosynthese und des –abbaus, sowie zahlreicher Transportprozesse kodieren. Die Expressionslevel der Zwillings-sRNAs hängen von der Wachstumsphase der Bakterien und dem Wachstumsmedium ab. Das weist darauf hin, dass NgncR_162 und NgncR_163 eine Rolle bei der Adaptation des Stoffwechsels von Gonokokken zu bestimmten Wachstumsbedingungen spielen. In dieser Arbeit wird zudem die Charakterisierung der sRNA NgncR_237 initiiert. Im Rahmen von in silico Analysen wurde die Sequenzkonservierung und mögliche Sekundärstruktur untersucht. Eine Kombination aus in silico Zielgen-Vorhersage und differentieller RNA Sequenzierung führte zur Identifizierung zahlreicher Zielgene, die in der Biogenese von Typ IV Pili und DNA Rekombination eine Rolle spielen. Allerdings konnten keine Induktionsbedingungen für die sRNA Expression gefunden werden. Interessanterweise konnte eine mögliche Zwillings-sRNA identifiziert werden, die dieselbe Targetinteraktionsdomäne wie NgncR_237 hat und somit dieselben Zielgene regulieren könnte. Zusammenfassend ermöglicht diese Arbeit neue Einblicke in die Genregulation durch nicht-kodierende RNAs in Gonokokken, indem zwei Paare Zwillings-sRNAs analysiert wurden, die den bakteriellen Stoffwechsel anpassen oder möglicherweise eine Rolle in der Typ IV Pilus Biogenese spielen.

Le virus de l'hépatite B (VHB) reste un problème de santé majeur dans le monde malgré la disponibilité du vaccin. Le VHB n’est pas éradiqué par les thérapies actuelles et 240 millions de personnes infectées chroniquement restent à risque de développer une cirrhose du foie et un carcinome hépatocellulaire (CHC).Le VHB est un petit virus hépatotrope doté d'un génome à ADN double brin partiel (ADNrc). Après infection l'ADNrc est converti en ADN épisomal (ADNccc) qui est ensuite organisé en minichromosome viral, qui est le modèle pour la transcription et qui initie la réplication. La protéine de l'hépatite B x (HBx) est recrutée sur l'ADNccc pour initier et maintenir la transcription de l'ADN ccc. HBx cible aussi directement des gènes cellulaires impliqué dans le développement du CHC.Nous avons utilisé une approche ChIP-Seq pour identifier toutes les cibles génomiques de HBx dans les cellules qui répliquent le VHB. Les cibles HBx sont à la fois des gènes codant les protéines et des ARNnc (75 miARN et 34 lncRNA). Nous avons montré que HBx réprimait un sous-ensemble de miARNs qui réguleraient négativement la réplication virale (ex : miR-24) et des miARNs impliqués dans le développement du CHC (ex : miR-21). Parmi les lncARNs ciblés pour HBx, nous avons étudié DLEU2, qui est fortement surexprimé dans l’infection par le VHB et le CHC. Nous avons en outre montré que DLEU2 lie à la fois HBx et l’histone méthyltransférase Ezh2, la sous-unité catalytique du complexe répressif PRC2. L'interaction avec DLEU2 et HBx relie les fonctions Ezh2/PRC2 conduisant à l'activation constitutive d'un sous-ensemble de gènes cibles d'Ezh2 qui sont normalement conservés dans un état réprimé. Nous avons également montré que l’interaction de HBx avec DLEU2 se produisait sur le minichromosome de l’ADNccc où elle stimulait la transcription/réplication du virus. Enfin, nous avons caractérisé par ATAC-Seq les changements d'accessibilité de la chromatine imposés par HBV dans les hépatocytes humains primaires / Hepatitis B virus (HBV) remains a major health problem worldwide despite the availability of the vaccine. No cure is available for the 240 million peoples chronically infected with HBV that are at risk to develop liver cirrhosis and hepatocellular carcinoma (HCC). Viral suppression, achieved by long term treatment with nucleotides analogues (NUCs), impacts on liver fibrosis and prevents liver decompensation but HCC risk is not reduced in the first 5 years of treatment. HBV is a small hepatotropic virus with a partially double strand DNA (rcDNA) genome. After hepatocyte infection the rcDNA is converted into the cccDNA episome that is then organized into a viral minichromosome that is the template for all viral transcripts and initiates replication. The hepatitis B x protein (HBx) is recruited on the cccDNA and is required to launch and maintain cccDNA transcription. HBx has also been shown to directly target cellular genes and this has been related to HCC development.We used a ChIP-Seq approach to determine the full repertoire of HBx genomic targets in HBV replicating cells. HBx targets include both protein coding genes and ncRNA (75 miRNAs and 34 lncRNAs). We showed that HBx represses a subset of miRNAs that would negatively regulate viral replication (i.e. miR-24) and miRNAs involved in HCC development (i.e. miR-21). Among the HBx targeted lncRNAs we focused DLEU2, which is strongly upregulated in HBV infection and HCC. We further showed that DLEU2 binds both HBx the Ezh2 histone methyltransferase, the catalytic subunit of the repressive PRC2 complex. The interaction with DLEU2 and HBx re-wires Ezh2/PRC2 functions leading to the constitutive activation of a subset of Ezh2 target genes that are normally kept in a repressed state. We also showed that HBx interaction with DLEU2 occurs on the cccDNA minichromosome where it boosts HBV transcription/replication. Finally, we characterized by ATAC-Seq HBV imposed changes of chromatin accessibility in primary human hepatocytes

Thesis (MScMedSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The role of bacterial small RNA (sRNA), i.e. RNA species between 50-500bp in size, in virulence, pathogenesis and drug resistance is gaining interest. In some bacterial species, it had been shown to play a crucial role in bacterial transcriptional and post-transcriptional regulation. sRNAs from various pathogenic bacteria were shown to modulate bacterial responses to the host and environment. In Mycobacterium tuberculosis, the causative agent of tuberculosis, more than 1000 sRNA species have been identified already; but the role of these sRNA in pathogenesis, virulence and stress responses is not well studied. Central dogma suggests that drug resistance in M. tuberculosis is associated with mutations in specific genes. However, a number of clinical drug resistant isolates do not harbour mutations in these genes, implicating other factors such as unknown mutations, as well as altered regulation of these resistance genes. Prediction of resistance, using molecular methods, can therefore be inaccurate in cases where known mutations are absent. In cases where known drug-resistance associated mutations are absent, mutations in other genes that regulate such resistance-associated genes might influence drug resistance. Growing evidence, in other bacteria and M. tuberculosis, hints at a role for mutations in intergenic regions and sRNAs species to play a role in bacterial growth and drug sensitivity. In light of this we hypothesised that mutations in sequences encoding sRNA or in sRNA target sequences influence the phenotype of M. tuberculosis clinical isolates. Using previously identified sRNA genes; we screened a genomic bank of clinical M. tuberculosis isolates for the presence of mutations in these sRNA encoding genes. A large number of isolates showed mutations in genes encoding for sRNAs. Furthermore, over-expression of sRNA using the plasmid pMV306 in Mycobacterium smegmatis showed differences in growth indicating that the presence of the extra copies of the three sRNA (mcr3, ASpks and mpr6) had a phenotypic effect on the bacterium. Overexpressed sRNAs did not affect the bacterial drug resistance phenotypes, although this requires further investigation before concluding the effect of sRNAs on drug resistance. We successfully modified a method to extract and purify sRNAs from Mycobacterium species, clean enough to perform Real Time Polymerase Chain Reaction even with small amounts. However challenges were faced in terms of quantification. Another challenge that still remains is obtaining reference genes specifically for sRNAs as we currently have none. / AFRIKAANSE OPSOMMING: Die rol van klein ribonukleïnsure ( m.a.w RNS spesies van ongeveer 50-250bp in grootte) in bakteriële virulensie, patogenese en antibiotika weerstandigheid word al hoe meer bevraagteken. 'n Rol vir hierdie nukleinsure in transkripsie en post-transkripsie regulering was voorheen gewys in verskeie bakteriële studies, waar dit gedemonstreer was dat hierdie RNA spesies n rol speel vir die bakterieë om aan te pas in die gasheer se omgewing 1–3. Meer as 1000 klein RNS spesies is voorheen in Mycobacterium tuberculosis (die bakterie wat tuberkulosis veroorsaak) geïdentifiseer, maar die rol van hierdie RNA in patogenese, virulensie en stress reaksies is nie bekend nie. Antibiotika weerstandigheid in M. tuberculosis word tans geassosieer met mutasies in spesifieke gene. Daar is wel n aantal weerstandige isolate waar hierdie bekende mutasies heeltemal afwesig is, wat suggereer dat ander rolspelers aanleiding kan gee to middelweerstandigheid. Byvoorbeeld, veranderde regulering van transkripsie patrone van gene (wat n bekende rol in weerstandigheid het) mag ook aanleiding gee tot weerstandigheid, maar sulke alternatiewe meganismes is nog nie goed ondersoek in die bakterium nie. Dis belangrik om al die rolspelers te identifiseer, want bestaande molekulere diagnostiese tegnieke fokus slegs op bekende gene; dus sal weerstandigheid gemis word in isolate waar bekende mutasies afwesig is en slegs molekulere tegnieke gebruik word. Die potensiële assosiasie van klein RNS in tuberkulose antibiotika weerstandigheid is voorheen in n paar studies gemaak. In lig van hierdie studies, is dit voorspel dat mutasies in klein RNA kan aanleiding gee tot verandering in die sensitiwiteit teenoor antibiotika in M. tuberculosis. Vir hierdie studie het ons n genoom bank, wat bestaan uit individuele genome van kliniese M.tuberculosis isolate, geanaliseer vir die teenwoordigheid van mutasies in klein RNS. Daar was spesifiek gefokus op die klein RNS spesies wat in vorige studies met antibiotika weerstandigheid geassosieer was. Hierdie bio-informatiese analise het mutasies in klein RNS spesies in n groot aantal weerstandige stamme geïdentifiseer. Hierdie mutasies was nie in sensitiewe isolate gevind nie, Om die rol van spesieke RNS spesies te ondersoek, was rekombinante plasmiede geskep wat bestaan het uit spesifieke klein RNS spesies van M. tuberculosis en die plasmied pMV306. Hierdie rekombinante was getransformeer in Mycobacterium smegmatis. Die teenwoordigheid van hierdie M. tuberculosis klein RNS kopieë in M.smegmatis het n negatiewe impak gehad op groei, en dui aan dat hierdie RNA spesies, naamlik mcr3, ASpks and mpr6, n potensiele belangrike rol het in die fenotipe van mikobakterieë het. Die ekstra kopieë het nie veranderinge veroorsaak in sensitiwiteit van M.smegmatis teenoor die antibiotika moksifloksasien en kanamisien nie, hoewel meer studies gedoen moet word voordat definitiewe konklusies gemaak kan word. In die finale deel van die studie, is n metode ontwerp om klein RNS op n makliker,vinner manier te isoleer van mikobakterieë. Hierdie metode was suksesvol aangewend om DNA-vry, hoë kwaliteit RNS, beide groter RNA en klein RNS spesies te isoleer. Die klein RNS was goeie kwaliteit, DNA-vry en kon omskep word in DNA met retrotranskripsie. Laasgenoemde DNA kon ook gebruik word in verder polymerase kettingreaksies. Dit het dus potential vir kwantitatiewe studies om die regulering van klein RNS te studeer.

Nespas is the non-coding antisense transcript of the imprinted Gnas cluster; it is expressed from the paternal allele and is located on mouse distal chromosome 2. In this thesis new transcripts of >10 kb and 0.8 kb have been identified. The 0.8 kb transcript is a spliced variant that is retained in the nucleus and its 3’ end lies approximately 30 kb from the start site. Transcription from the Nespas promoter does not proceed beyond this point. A collection of previously known splice variants have also been detected and are exported to the cytoplasm. Nespas is expressed in the embryo during the second half of gestation and peaks at 13.5 dpc. Nespas is imprinted in the placenta at 11.5, 15.5 and 17.5 dpc. The Nespastm4Jop allele, to truncate the Nespas transcript 10.5 kb from the start site, has been transmitted through the germline and a breeding colony established. Preliminary analysis shows Nespas has a regulatory function. A second targeting construct to truncate Nespas 12.5 kb from the start site has been designed and assembled to investigate whether the 3’ end of the Nespas transcript that is transcribed upstream of the Nesp promoter is required for Nespas-mediated silencing of Nesp.

University of Macau / Institute of Chinese Medical Sciences

Pancreatic cancer is an abhorrent malignancy with limited diagnostics and response to drug therapy. It is believed that noncoding RNAs (ncRNAs) will further the understanding behind the mechanisms of pancreatic cancer development and progression, providing a novel approach for drug development and biomarker discovery. Therefore, a database of pancreatic cancer ncRNAs was established using bioinformatics and text mining approaches. These ncRNAs were characterized for RNA expression, copy number variation, disease association, single nucleotide polymorphisms, secretome analysis, and identification of protein targets. Exosomal proteins and ncRNA identified through this study provide the basis for noninvasive diagnostic potential. Additionally, a secreted microRNA, MIR3620, emerged from this study as a potential prognostic and diagnostic biomarker for pancreatic cancer. By analyzing MIR3620 and its protein targets, a mechanism of regulation for these genes in contributing to the progression and development of pancreatic cancer was established. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Friedreich ataxia (FRDA) is a neurodegenerative disorder that is inherited in an autosomal recessive pattern. The most common FRDA mutation is hyperexpansion of a GAA triplet repeat sequence in the first intron of the affected gene, frataxin (FXN), resulting in decreased frataxin protein expression. The hyperexpanded GAA repeats can adopt unusual DNA structures and induce aberrant epigenetic changes leading to heterochromatin mediated gene silencing. Several epigenetic changes, including increased levels of DNA methylation, histone modifications, repressive chromatin formation and elevated levels of non-coding RNA have been reported in FRDA. It has been reported that a novel FXN antisense transcript (FAST-1), is present at higher levels in FRDA patient-derived fibroblasts and its overexpression is associated with the depletion of CTCF, a chromatin insulator protein, and heterochromatin formation involving the critical +1 nucleosome. Previously, characteristics of FAST-1 were investigated in our lab and a full-length FAST-1 transcript containing a poly (A) tail was identified. To investigate any possible effects of FAST-1 on FXN expression, I first overexpressed this FAST-1 transcript in three different non-FRDA cell lines and a consistent decrease of FXN expression was observed in each cell type compared to control cells. I also identified that FAST-1 copy number is positively correlated with increased FAST-1 expression, which in turn is negatively correlated with FXN expression in FAST-1 overexpressing cells. Additionally, we found that FAST-1 overexpression is associated with increased levels of DNA methylation at CpG sites U6 and U11 of the FXN upstream GAA repeat region, together with CTCF depletion and heterochromatin formation at the 5'UTR of the FXN gene. To further investigate the role of FAST-1 in FXN gene silencing, I used a small hairpin RNA (shRNA) strategy to knock down FAST-1 expression in FRDA fibroblast cells. I found that knocking down FAST-1 increases FXN expression, but not to the level of control cells. Lastly, I investigated the pattern of FAST-1 expression and histone modifications at the FXN transgene in our new FRDA mouse model, designated YG8LR. The YG8LR mice showed decreased levels of FXN expression and H3K9ac and increased levels of FAST-1 expression and H3K9me3. Our data suggest that since FAST-1 is associated with FXN gene silencing, inhibition of FAST-1 may be an approach for FRDA therapy.

Non-coding RNAs (ncRNAs) are a subset of RNAs that do not code for protein. They are divided into a number of different groups based on their function and targets. Small nucleolar RNAs (snoRNAs) are ncRNAs that have long been known to function as guides for ribosomal RNA (rRNA) modifying enzymes. They are classified into two major groups: box C/D snoRNAs and box H/ACA snoRNAs. Most box C/D snoRNAs direct the 2'-O-methylation of rRNA substrates, but some lack known targets and are therefore termed 'orphan snoRNAs'. Studies have implicated orphan snoRNAs in pre-mRNA processing and stability, but the functional consequence of snoRNA binding to mRNAs has not been fully determined. Saccharomyces cerevisiae had two orphan snoRNAs, snR4 and snR45, with no known function in ribosome synthesis. This project aimed to determine the targets of these snoRNAs, and investigate the effects of snoRNA binding to non-canonical target RNAs, as well as the underlying mechanism. Synthetic gene array screens with deletions of the SNR4 and SNR45 genes identified multiple positive and negative genetic interactions. In particular, deletion of either snoRNA gene was synthetic-lethal with mutation of the snoRNA-associated methyltransferase, Nop1 (Fibrillarin in humans), demonstrating that both have important functions. CLASH analyses of RNA-RNA interactions showed that these snoRNAs bind multiple mRNAs, while RNA sequencing and RT-qPCR revealed that snoRNA deletion altered mRNA abundance. Both orphan snoRNAs were well conserved between fungi, with a region of high conservation indicating a potential binding site. Associations were identified between snR4 and snR45 and multiple sequences within rRNA, including two recently identified sites of 18S rRNA acetylation. Work elsewhere showed that snR4 and snR45 function as guides for the acetyltransferase Kre33 using the region of high conservation, removing their 'orphan' status. Orphan snoRNAs have been implicated in human diseases, such as Prader Willi Syndrome and cancers. The work discussed in this thesis helps to elucidate the RNA interactions of yeast orphan snoRNAs. It has provided a greater understanding of the mechanisms involved, and may inform future work in combatting human disease.