Yin Yang 1 (YY1) is a multifunctional transcription factor that is known mainly for its ability to activate or initiate transcription of a wide assortment of genes involved in cellular growth and differentiation. <i>Xenopus laevis </i>oocytes and embryos were used as a model to identify and characterize a potential developmental role for YY1. Northern and Western blots of oocyte and embryonic extracts showed YY1 mRNA and protein is expressed from the earliest stages of oocyte development through to tadpole stages. Examination of the transcriptional activity of YY1 in both oocytes and embryos using reporter gene constructs containing YY1-binding elements demonstrated that YY1 does not act as a repressor or activator of transcription either in oocytes or in embryos. Sub-cellular fractionation of oocytes and Western blot analysis showed YY1 is localized almost exclusively to the cytoplasm of oocytes and in cells of early embryos. Sequence analysis of YY1 revealed that it contains an established RNA binding motif located within the zinc fingers. A series of biochemical assays were performed to address the possibility that YY1 functions as a component of mRNPs in the oocyte cytoplasm. RNA gel mobility shift analyses using in vitro synthesized histone H2A transcripts and supershifts using YY1-specific antibodies suggested that YY1 or YY1-containing complexes in cytoplasmic extracts were able to bind RNA. Chromatographic analysis of oocyte lysates showed YY1 was specifically retained on oligo (dT) cellulose columns. Treatment of the same lysates with RNase abolished binding to oligo (dT), indicating that retention is dependent on the presence of intact polyadenylated RNAs. This suggested that YY1 may be a component of messenger ribonucleoprotein particles (mRNP). Separation of oocyte lysates by size exclusion chromatography (SEC) revealed that YY1 was present in large complexes with an approximate molecular mass of 480 kDa. RNase or phosphatase treatment of oocyte extracts released YY1 from high mass complexes. Analysis of phosphatase or RNase-treated extracts for DNA binding activity showed that monomeric YY1 was able to bind DNA with high affinity. Immunoprecipitation of YY1 complexes followed by cDNA synthesis and sequencing revealed that YY1 is associated with both ribosomal and messenger RNAs in the cytoplasm of the oocyte. These results indicate a novel function for YY1 as a component of messenger ribonucleoprotein particles.

Yin Yang 1 (YY1) is a multifunctional transcription factor that is known mainly for its ability to activate or initiate transcription of a wide assortment of genes involved in cellular growth and differentiation. <i>Xenopus laevis </i>oocytes and embryos were used as a model to identify and characterize a potential developmental role for YY1. Northern and Western blots of oocyte and embryonic extracts showed YY1 mRNA and protein is expressed from the earliest stages of oocyte development through to tadpole stages. Examination of the transcriptional activity of YY1 in both oocytes and embryos using reporter gene constructs containing YY1-binding elements demonstrated that YY1 does not act as a repressor or activator of transcription either in oocytes or in embryos. Sub-cellular fractionation of oocytes and Western blot analysis showed YY1 is localized almost exclusively to the cytoplasm of oocytes and in cells of early embryos. Sequence analysis of YY1 revealed that it contains an established RNA binding motif located within the zinc fingers. A series of biochemical assays were performed to address the possibility that YY1 functions as a component of mRNPs in the oocyte cytoplasm. RNA gel mobility shift analyses using in vitro synthesized histone H2A transcripts and supershifts using YY1-specific antibodies suggested that YY1 or YY1-containing complexes in cytoplasmic extracts were able to bind RNA. Chromatographic analysis of oocyte lysates showed YY1 was specifically retained on oligo (dT) cellulose columns. Treatment of the same lysates with RNase abolished binding to oligo (dT), indicating that retention is dependent on the presence of intact polyadenylated RNAs. This suggested that YY1 may be a component of messenger ribonucleoprotein particles (mRNP). Separation of oocyte lysates by size exclusion chromatography (SEC) revealed that YY1 was present in large complexes with an approximate molecular mass of 480 kDa. RNase or phosphatase treatment of oocyte extracts released YY1 from high mass complexes. Analysis of phosphatase or RNase-treated extracts for DNA binding activity showed that monomeric YY1 was able to bind DNA with high affinity. Immunoprecipitation of YY1 complexes followed by cDNA synthesis and sequencing revealed that YY1 is associated with both ribosomal and messenger RNAs in the cytoplasm of the oocyte. These results indicate a novel function for YY1 as a component of messenger ribonucleoprotein particles.

Late SV40 factor (LSF) is a CP2 family transcription factor involved in cell cycle regulation. In liver cancer, LSF is an oncogene, in part due to its role in upregulation of osteopontin leading to increase tumor size. As a result, LSF is a potential target for drug discovery. LSF binds the p65 subunit of the transcription factor NFkB and also the transcription factor ying yang 1 (YY1). In this thesis, I show that binding of both YY1 and p65 occurs at the ubiquitin-like domain of LSF in U2OS cell extracts. Interestingly, when phosphatase inhibitors are added during preparation of U2OS cell extracts, the binding of YY1 and p65 to LSF shifts from the ubiquitin-like domain of LSF to the DNA binding domain. The role of a yet unidentified docking protein may be responsible for this shift in binding. In an attempt to map the specific region of the LSF sequence that is involved in these interactions, I have developed a peptide identification assay which utilizes protease digestion, protein mediated peptide capture, and LC ESI-MS. Through the use of this assay, I'm confident that the sequence(s) involved in these LSF protein-protein interactions can be further defined.

Le cancer du sein est le cancer le plus fréquent chez la femme (Boyle and Ferlay, 2005; Ferlay et al., 2007). Même si les traitements sont de plus en plus efficaces, il est responsable denviron 130 000 décès en Europe. Environ 20-30% des cancers du sein surexprime le gène ERBB2. Cette surexpression confère à la cellule un profil tumoral très agressif, et résistant aux chimiothérapies conventionnelles. Létude des facteurs responsable de la surexpression du gène ERBB2 dans les cancers du sein est le thème principal de recherche du laboratoire doncologie moléculaire. Notre laboratoire, a étudié les mécanismes moléculaires responsables de la surexpression du gène ERBB2 dans les cancers du sein. Nous avons montré que la surexpression est la conséquence dune stimulation de la transcription et non de la stabilisation de lARN (Pasleau et al., 1993). Pour étudier la régulation de la transcription un fragment de 6 kb du promoteur du gène ERBB2 a été cloné et séquencé. Différentes régions régulatrices ont été identifiées (Grooteclaes et al., 1994). Plusieurs sites de liaison pour des facteurs AP-2 ont été identifiés (Delacroix et al., 2005; Grooteclaes et al., 1999; Vernimmen et al., 2003a). La fixation des facteurs au promoteur a été vérifiée par Chromatin Immuniprecipitation (ChIP assay) (Begon et al., 2005; Delacroix et al., 2005). Afin de mieux comprendre le fonctionnement des facteurs de transcription AP-2, nous avons cherché les protéines interagissant avec ce facteur et contribuant à la surexpression dERBB2 dans des lignées de cancer du sein. Précédemment, Dominique Begon a montré linteraction de la protéine YY1 avec le facteur de transcription AP-2α et leur implication sur le promoteur du gène ERBB2 (Begon et al., 2005). La première partie de mon travail a été de mettre en corrélation par immunohistochimie lexpression des protéines YY1 et AP-2α avec la surexpression dERBB2 dans des tumeurs primaires. Nous avons également voulu étudier leffet dune diminution des protéines YY1 et AP-2 sur lexpression dERBB2, à laide de siRNAs (Voir article 1 en annexe, (Allouche A and Nolens G. et al., 2008). La deuxième partie de ce travail a porté sur lidentification dautres protéines pouvant interagir avec les protéines AP-2. Après purification, les protéines Ku70 et Ku80 furent identifiées. Nous avons voulu étudier leffet de cette interaction sur lactivité des protéines AP-2 (α et γ) et sur lexpression dERBB2 (voir article 2 en annexe).

Early embryonic development in vertebrates is directed in part by maternal mRNAs expressed in oocytes and stored in cytoplasmic messenger ribonucleoprotein particles (mRNPs). Abundant evidence demonstrates the importance of mRNPs in embryonic development and in post-embryonic cellular function; however their characterization has been hampered by lack of suitable methodologies. The Xenopus oocyte has been the primary model system for studies of mRNPs. YY1 is a well-studied transcriptional regulatory factor that is sequestered in the oocyte cytoplasm and present entirely in cytoplasmic oocyte mRNPs. The objective of this thesis was to examine the biochemistry of YY1 association with maternal mRNA molecules in order to shed light on the role of YY1 in development and the poorly understood biology of oocyte mRNPs. The initial working hypotheses were that association of YY1 with mRNPs is dependent on sequence-specific RNA-binding activity and, therefore, that YY1 associates with a definite subset of maternal mRNA. A number of unique methods were developed in this study to address these hypotheses. RNA immunoprecipitation-DNA microarray (RIP-CHIP) analysis establishes that YY1 associates with a subset of mRNAs in the oocyte pool. A novel sequence-specific RNA-binding activity of the YY1 protein is demonstrated, and the RNA-binding activity of YY1 is shown to be required for its association with oocyte mRNPs in vivo. The functional roles of YY1 mRNA substrates are discussed in the context of embryological development and the biological function of YY1 in oocyte mRNPs. Extension of the experimental approaches developed in this thesis to the entire set of mRNP proteins would significantly advance our understanding of mRNP composition and heterogeneity, as well as the biological function of maternal mRNAs and mRNPs in development.

Early embryonic development in vertebrates is directed in part by maternal mRNAs expressed in oocytes and stored in cytoplasmic messenger ribonucleoprotein particles (mRNPs). Abundant evidence demonstrates the importance of mRNPs in embryonic development and in post-embryonic cellular function; however their characterization has been hampered by lack of suitable methodologies. The Xenopus oocyte has been the primary model system for studies of mRNPs. YY1 is a well-studied transcriptional regulatory factor that is sequestered in the oocyte cytoplasm and present entirely in cytoplasmic oocyte mRNPs. The objective of this thesis was to examine the biochemistry of YY1 association with maternal mRNA molecules in order to shed light on the role of YY1 in development and the poorly understood biology of oocyte mRNPs. The initial working hypotheses were that association of YY1 with mRNPs is dependent on sequence-specific RNA-binding activity and, therefore, that YY1 associates with a definite subset of maternal mRNA. A number of unique methods were developed in this study to address these hypotheses. RNA immunoprecipitation-DNA microarray (RIP-CHIP) analysis establishes that YY1 associates with a subset of mRNAs in the oocyte pool. A novel sequence-specific RNA-binding activity of the YY1 protein is demonstrated, and the RNA-binding activity of YY1 is shown to be required for its association with oocyte mRNPs in vivo. The functional roles of YY1 mRNA substrates are discussed in the context of embryological development and the biological function of YY1 in oocyte mRNPs. Extension of the experimental approaches developed in this thesis to the entire set of mRNP proteins would significantly advance our understanding of mRNP composition and heterogeneity, as well as the biological function of maternal mRNAs and mRNPs in development.

Thesis (Ph.D.)--University of South Florida, 2001. / Includes vita. Includes bibliographical references (leaves 80-104). Also available online.

Inflammation is a homeostatic response to tissue injury or infection, which is normally short- lived and quickly resolves to limit tissue damage. In contrast, chronic inflammation has been linked to a variety of human diseases, including cancers such as glioblastoma multiforme (GBM). GBMs are very aggressive tumors with very low patient survival rates, which have not improved in several decades. GBM tumors are characterized by necrosis and profound inflammation; with cytokines secreted by both GBM cells and the tumor microenvironment. The mechanisms by which chronic inflammation develops and persists in GBM regardless of multiple anti-inflammatory feedback loops remain elusive. This project identifies a molecular switch which promotes chronic inflammation in GBM, but not primary human astrocytes.

Yin Yang 1 (YY1) is a sequence-specific DNA binding transcription factor that plays an important role in development and differentiation. It activates or represses many genes during cell growth and differentiation and is also required for the normal development of the mammalian embryo. Moreover, it has been shown that YY1 may function as a transcriptional initiator. In this dissertation, regulation of human YY1 is analyzed systematically at three levels: At the genomic level, one major transcriptional initiation site of the YY1 gene was mapped to 478 bp upstream of the ATG translational start site. The YY1 promoter was localized to within 277 bp upstream of the major transcriptional initiation site and was shown to contain multiple binding sites for transcriptional factor Sp1 but lack a consensus TATA box. Overexpression of the adenovirus E1A protein represses expression of the YY1 promoter. At the polypeptide level, the activity of YY1 is regulated through acetylation by p300 and PCAF and deacetylation by HDACs. YY1 was acetylated in two regions: both p300 and PCAF acetylated the central glycine/lysine-rich domain of residues 170- 200, and PCAF also acetylated YY1 at the C-terminal DNA-binding domain. Acetylation of the central region was required for the full transcriptional repression activity of YY1 and targeted YY1 for active deacetylation by HDACs. However, the C-terminal region of YY1 could not be deacetylated. Rather, the acetylated Cterminal region interacted with HDACs, which resulted in stable histone deacetylase activity associated with the YY1 protein. Furthermore, acetylation of the C-terminal domain decreased the DNA binding activity of YY1. At the protein complex level, YY1 was shown to form a complex with up to four different proteins consistently throughout different purification methods. These proteins are likely to have important regulatory roles in the transcriptional activity of YY1. Taken together, these findings will provide valuable information to our understanding of the regulatory mechanisms of transcription in general.

骨骼肌分化是由一个包括转录因子、表观遗传调控子和非编码RNA在内的复杂网络共同调控的。YY1能够通过募集PRC2抑制一系列肌肉结构基因的表达，进而抑制肌肉分化。miRNA是一组转录后调控基因表达的小片段非编码RNA，miRNA与转录因子的相互作用已经被广泛证实。在本次研究中，我们证实了一个YY1和肌肉特异性miRNA（miR-1,miR-133和miR-206）的调控回路。实验证实，YY1通过肌肉特异性miRNA增强子区域的YY1结合位点募集PRC2来抑制肌肉特异性miRNA的表达。YY1调控miR-1在体外和体内肌肉分化均被证实有重要意义。另外，我们还证实miR-1能够负反馈作用于YY1，抑制YY1的表达。 / 为了阐述YY1在基因组转录中的作用，我们做了肌肉中YY1的ChIP-seq。测序结果表明在C2C12肌肉母细胞中有1820个YY1结合位点，其中很大部分位于基因间的区域。进一步研究发现，基因间YY1的结合可能调控一些lincRNA，而这些lincRNA在肌肉发育的作用目前尚不清楚。进一步研究这些可能受YY1调节的lincRNA，我们证实了YY1能够正调控两个新的lincRNA，YAM-1和YAM-2。YAM-1在肌肉分化过程中逐渐下调，并且通过正调控他的临近基因miR-715，抑制肌肉分化，而YAM-2能够促进早期的肌肉分化。 / 总之，我们第一次在肌肉细胞中进行了YY1的ChIP-seq，并且证实在肌肉分化过程中转录因子和非编码RNA相互作用的重要性和普遍性。 / Skeletal muscle cell differentiation is a process orchestrated by a complex network of transcription factors, epigenetic regulators and non-coding RNAs. As a repressor of myogenesis, Yin Yang 1 (YY1) silences a number of muscle structural genes through recruiting Polycomb repressive complex2 (PRC2) in proliferating myoblasts. microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression post-transcriptionally, and mounting evidences support the prevalence and functional significance of their interplay with transcription factors (TFs). Here we describe the identification of a regulatory circuit between muscle miRNAs (miR-1, miR-133 and miR-206) and Yin Yang 1 (YY1). The subsequent experimental results demonstrate that YY1 indeed represses muscle miRs expression in myoblasts and the repression is mediated through multiple enhancers and recruitment of Polycomb complex to several YY1 binding sites. YY1 regulating miR-1 is functionally important for both in vitro and in vivo myogenesis. Furthermore, we demonstrate that miR-1 in turn targets YY1, thus forming a negative feedback loop. / To elucidate its role on genome-wide regulation of transcription, here in the second part of this study we performed ChIP-Seq for YY1 in muscle cells. Our results revealed 1820 YY1 binding peaks genome-wide in myoblasts, with a large portion residing in the intergenic region. A close analysis of the intergenic region bound by YY1 uncovered that YY1 may regulate a large number of lincRNAs (Long Intergenic non-coding RNAs), whose roles in skeletal myogenesis have not been explored yet. As further elucidation of the functional roles of YY1-lincRNA regulation, we identified two novel lincRNAs, YAM-1 and YAM-2 as positively regulated by YY1. YAM-1 was found to be down-regulated upon myogenic differentiation and acts as an inhibitor of myoblast differentiation. We further demonstrated that YAM-1 functions by its in cis regulation on a downstream gene, miR-715 which promotes differentiation. YAM-2, on the other hand, appears to promote myogenesis. / Together, our studies not only provide the first genome-wide picture of YY1 association in muscle cells but also uncovered novel regulatory circuits required for skeletal myogenesis and reinforce the idea that regulatory circuitry involving non-coding RNAs and TFs is essential components of myogenic regulatory network. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Lu, Leina. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 144-167). / Abstract also in Chinese. / Abstract / 摘要 / Acknowledgement / Publications / List of figures / List of tables / Abbreviations / Table of content / Chapter Chapter 1: --- INTRODUCTION / Chapter 1.1 --- Skeletal Myogenesis --- p.1 / Chapter 1.2 --- Transcriptional Regulation of myogenic differentiation --- p.3 / Chapter 1.2.1 --- Transcriptional regulatory network in myogenic differentiation --- p.3 / Chapter 1.2.2 --- YY1 as a transcription factor in myogenic differentiation --- p.5 / Chapter 1.3 --- Epigenetic Regulation during skeletal muscle differentiation --- p.6 / Chapter 1.4 --- microRNA: Post-transcriptional regulation on myogenic differentiation --- p.11 / Chapter 1.4.1 --- Muscle specific miRNAs in skeletal myogenic differentiation --- p.15 / Chapter 1.4.2 --- Non-muscle specific miRNAs in skeletal myogenic differentiation --- p.20 / Chapter 1.4.3 --- miRNAs and skeletal muscle diseases --- p.23 / Chapter 1.5 --- Long Non-coding RNAs --- p.26 / Chapter 1.5.1 --- Long Non-coding RNAs and lincRNAs --- p.26 / Chapter 1.5.2 --- LincRNAs in muscles --- p.30 / Chapter Chapter 2: --- MATERIALS AND METHODS / Chapter 2.1 --- C2C12 cell line --- p.32 / Chapter 2.2 --- Primary Myoblast isolation and in vitro culture --- p.32 / Chapter 2.3 --- Animal studies --- p.33 / Chapter 2.4 --- RNA extraction --- p.34 / Chapter 2.5 --- RT-PCR and Real-Time RT-PCR --- p.35 / Chapter 2.6 --- Transfection and infection --- p.37 / Chapter 2.7 --- Oligonucleotides --- p.38 / Chapter 2.8 --- Dual-luciferase reporter assay --- p.43 / Chapter 2.9 --- Immunofluorencence staining --- p.44 / Chapter 2.10 --- Antibodies --- p.45 / Chapter 2.11 --- Protein extraction and Western blotting --- p.46 / Chapter 2.12 --- DNA constructs --- p.48 / Chapter 2.13 --- Mutagenesis --- p.49 / Chapter 2.14 --- RNA-Fluorescence In Situ Hybridization (RNA-FISH) --- p.51 / Chapter 2.15 --- C2C12 cells with YY1-stably knocked down --- p.52 / Chapter 2.16 --- Rapid Amplification of cDNA Ends (RACE) --- p.53 / Chapter 2.17 --- Chromatin Immunoprecipitation (ChIP) --- p.55 / Chapter 2.18 --- ChIP-PCR --- p.58 / Chapter 2.19 --- ChIP-sequencing --- p.58 / Chapter 2.20 --- Northern blotting --- p.59 / Chapter 2.21 --- Prediction of miRNA targets --- p.60 / Chapter 2.22 --- Statistical analysis --- p.60 / Chapter Chapter 3: --- Results / Chapter 3.1 --- YY1-miR-1/133 regulatory circuitry in skeletal myogenesis --- p.61 / Chapter 3.1.1 --- YY1 decreases miR-1/133 during skeletal muscle differentiation --- p.61 / Chapter 3.1.1.1 --- Negative correlation between YY1 and miR-1/133 during C2C12 differentiation --- p.61 / Chapter 3.1.1.2 --- Negative correlation between YY1 and miR-1/133 in primary cell differentiation --- p.63 / Chapter 3.1.1.3 --- Negative correlation between YY1 and miR-1/133 in postnatal muscle development and mdx mouse model --- p.65 / Chapter 3.1.1.4 --- Deletion of YY1 upregulates miR-1/133 both in C1C12 and primary myoblast --- p.68 / Chapter 3.1.1.5 --- Deletion of YY1 upregulates miR-1/133 at the transcriptional level --- p.70 / Chapter 3.1.2 --- YY1 represses miR-1/133 by binding to 4 enhancers --- p.72 / Chapter 3.1.2.1 --- Four enhancers of miR-1/133 with potential YY1 targeting sites --- p.72 / Chapter 3.1.2.2 --- YY1 represses the four enhancers’ activities --- p.75 / Chapter 3.1.2.3 --- Depletion of YY1 up-regulates the four enhancers’ activities --- p.77 / Chapter 3.1.2.4 --- YY1 directly binds to the putative binding sites and mediates the repression on miR-1/133 --- p.79 / Chapter 3.1.2.5 --- YY1 recruits Ezh2 to the enhancers which subsequently causes histone modification --- p.82 / Chapter 3.1.3 --- YY1 repressing miR-1/133 is functionally significant in myogenesis --- p.84 / Chapter 3.1.3.1 --- Negative correlation between YY1 and miR-1/133 in CTX induced muscle regeneration model --- p.84 / Chapter 3.1.3.2 --- Depletion of YY1 in CTX induced muscle regeneration model promotes miR-1/133 expression --- p.87 / Chapter 3.1.3.3 --- Depletion of YY1 in CTX induced muscle regeneration model promotes muscle differentiation --- p.89 / Chapter 3.1.4 --- miR-1 can target YY1 forming a feedback loop --- p.92 / Chapter 3.1.5 --- miR-1 can repress Pax7 by targeting two binding sites on 3’UTR --- p.95 / Chapter 3.1.5.1 --- miR-1 targets Pax7 by binding to two target sites --- p.95 / Chapter 3.1.5.2 --- miR-1 represses Pax7 forming an YY1-miR-1-Pax7 regulating circuitry in skeletal myogenesis --- p.98 / Chapter 3.1.6 --- Conclusion: YY1-miR-1-Pax7 regulatory circuitry in skeletal myogenesis --- p.100 / Chapter 3.2 --- ChIP-seq reveals YY1-lincRNA regulation in skeletal myogenesis --- p.102 / Chapter 3.2.1 --- ChIP-seq uncovered a large number of genes under YY1 regulation --- p.102 / Chapter 3.2.2 --- ChIP-seq reveals that YY1 associates with lincRNA loci --- p.105 / Chapter 3.2.2.1 --- YY1 associates with lincRNA-YAM loci --- p.105 / Chapter 3.2.2.2 --- YY1 positively regulates YAM-1 and YAM-2 both in vitro and in vivo --- p.107 / Chapter 3.2.3 --- YY1-YAM-1-miR-715 regulatory pathway in muscle differentiation --- p.109 / Chapter 3.2.3.1 --- Genomic organization and cellular localization of YAM-1 --- p.109 / Chapter 3.2.3.2 --- Expression of YAM-1 decreases during myogenic differentiation --- p.112 / Chapter 3.2.3.3 --- YAM-1 represses myogenic differentiation both in vitro and in vivo --- p.115 / Chapter 3.2.3.3.1 --- YAM-1 inhibits C2C12 differentiation --- p.115 / Chapter 3.2.3.3.2 --- YAM-1 inhibits muscle differentiation in vivo --- p.117 / Chapter 3.2.3.4 --- A functional YY1-YAM-1-miR-715 regulatory axis in skeletal myogenic differentiation --- p.119 / Chapter 3.2.3.4.1 --- miR-715 is down-regulated during muscle differentiation --- p.119 / Chapter 3.2.3.4.2 --- miR-715 is under the regulation of YY1-YAM-1 --- p.122 / Chapter 3.2.3.4.3 --- miR-715 represses muscle differentiation forming a YAM-1-miR-715 regulatory axis during muscle differentiation --- p.124 / Chapter 3.2.4 --- YAM-2 promotes early myogenic differentiation --- p.126 / Chapter 3.2.4.1 --- Genomic organization and cellular localization of YAM-2 --- p.126 / Chapter 3.2.4.2 --- YAM-2 is regulated during myogenic differentiation --- p.129 / Chapter 3.2.4.3 --- YAM-2 promotes early myogenic differentiation --- p.131 / Chapter Chapter 4: --- DISCUSSION / Chapter 4.1. --- YY1-miRNA regulatory circuit in skeletal myogenesis --- p.133 / Chapter 4.2 --- YY1 mediates epigenetic modification in skeletal myogenesis --- p.135 / Chapter 4.3 --- miRNAs in skeletal myogenesis --- p.136 / Chapter 4.4 --- YY1 regulates long intergenic non-coding RNAs in skeletal myogenesis --- p.138 / Chapter Chapter --- 5: SUMMARY AND FUTURE WORK --- p.142 / REFERENCE --- p.144