II tipo restrikcijos endonukleazės atpažįsta specifines DNR sekas ir kerpa DNR šiose sekose arba šalia jų. BpuJI, atpažįstanti 5’-CCCGT seką, skiriasi nuo kitų fermentų tuo, kad jos kirpimo vieta yra labai variabili. Čia parodoma, kad BpuJI yra dimeras, sudarytas iš dviejų monomerų, kurie turi po du atskirus domenus. BpuJI N domenas atpažįsta taikinį kaip monomeras, o C-domenas pasižymi nukleaziniu aktyvumu ir dimerizuojasi. Apo-fermento nukleazinis aktyvumas yra nuslopintas. N-domenams atpažinus taikinį, aktyvuojamas C-domenas, kuris perkerpa DNR šalia taikinio. Be to, aktyvuotas C-domenas yra nespecifinė nukleazė, linkusi nukirpti ~3 nt nuo buko dvigrandės DNR galo. Taigi, BpuJI DNR karpymo pobūdis yra labai sudėtingas. Bioinformatinė analizė ir kryptinga mutagenezė parodė, kad BpuJI C-domenas turi PD-(D/E)XK struktūrinę sanklodą ir yra panašus į archėjų Holidėjaus jungtis karpančias nukleazes. Išsprendus 1,3 Å skiriamosios gebos BpuJI N-domeno/DNR komplekso erdvinė struktūrą, paaiškėjo, kad šį domeną sudaro du „sparnuotą“ spiralė-linkis-spiralė motyvą turintys subdomenai. BpuJI taikinį atpažįsta aminorūgštys, esančios N-rankoje ir abiejų spiralė-linkis-spiralė motyvų atpažinimo spiralėse. BpuJI N-domenas yra labiausiai panašus į Nt.BspD6I nukleazę, kerpančią vieną DNR grandinę. Nt.BspD6I/DNR komplekso struktūros modelis rodo, kad Nt.BspD6I ir BpuJI taikinį atpažįstantys struktūriniai elementai yra panašūs. / Type II restriction endonucleases recognize specific DNA sequences and cleave DNA at fixed positions within or close to this sequence. BpuJI recognizes the 5’-CCCGT sequence, but in contrast to other enzymes its cleavage site is very variable. This study shows that BpuJI is a dimer in solution and consists of two separate domains. The N-domain binds to the target sequence as a monomer, while the C-domain is responsible for nuclease activity and dimerization. The nuclease activity is repressed in the apo-enzyme and becomes activated upon specific DNA binding by the N-domains. The activated C-domain cleaves DNA near the target site. In addition, it possesses an end-directed nuclease activity and preferentially cuts ~3 nt from the 3’ terminus. This leads to a very complicated pattern of DNA cleavage. Bioinformatics and mutational analysis revealed that the BpuJI C-domain harbours a PD (D/E)XK active site and is structurally related to archaeal Holliday junction resolvases. The crystal structure of the BpuJI N-domain bound to cognate DNA was solved at 1.3 Å resolution. It revealed two winged-helix subdomains, D1 and D2. The recognition of the target sequence is achieved the amino acid residues located on both the HTH motifs and an N-terminal arm. The BpuJI DNA recognition domain is most similar to the nicking endonuclease Nt.BspD6I. The modelling suggests that Nt.BspD6I could share the specificity-determining regions with BpuJI.

Type II restriction endonucleases recognize specific DNA sequences and cleave DNA at fixed positions within or close to this sequence. BpuJI recognizes the 5’-CCCGT sequence, but in contrast to other enzymes its cleavage site is very variable. This study shows that BpuJI is a dimer in solution and consists of two separate domains. The N-domain binds to the target sequence as a monomer, while the C-domain is responsible for nuclease activity and dimerization. The nuclease activity is repressed in the apo-enzyme and becomes activated upon specific DNA binding by the N-domains. The activated C-domain cleaves DNA near the target site. In addition, it possesses an end-directed nuclease activity and preferentially cuts ~3 nt from the 3’ terminus. This leads to a very complicated pattern of DNA cleavage. Bioinformatics and mutational analysis revealed that the BpuJI C-domain harbours a PD (D/E)XK active site and is structurally related to archaeal Holliday junction resolvases. The crystal structure of the BpuJI N-domain bound to cognate DNA was solved at 1.3 Å resolution. It revealed two winged-helix subdomains, D1 and D2. The recognition of the target sequence is achieved the amino acid residues located on both the HTH motifs and an N-terminal arm. The BpuJI DNA recognition domain is most similar to the nicking endonuclease Nt.BspD6I. The modelling suggests that Nt.BspD6I could share the specificity-determining regions with BpuJI. / II tipo restrikcijos endonukleazės atpažįsta specifines DNR sekas ir kerpa DNR šiose sekose arba šalia jų. BpuJI, atpažįstanti 5’-CCCGT seką, skiriasi nuo kitų fermentų tuo, kad jos kirpimo vieta yra labai variabili. Čia parodoma, kad BpuJI yra dimeras, sudarytas iš dviejų monomerų, kurie turi po du atskirus domenus. BpuJI N domenas atpažįsta taikinį kaip monomeras, o C-domenas pasižymi nukleaziniu aktyvumu ir dimerizuojasi. Apo-fermento nukleazinis aktyvumas yra nuslopintas. N-domenams atpažinus taikinį, aktyvuojamas C-domenas, kuris perkerpa DNR šalia taikinio. Be to, aktyvuotas C-domenas yra nespecifinė nukleazė, linkusi nukirpti ~3 nt nuo buko dvigrandės DNR galo. Taigi, BpuJI DNR karpymo pobūdis yra labai sudėtingas. Bioinformatinė analizė ir kryptinga mutagenezė parodė, kad BpuJI C-domenas turi PD-(D/E)XK struktūrinę sanklodą ir yra panašus į archėjų Holidėjaus jungtis karpančias nukleazes. Išsprendus 1,3 Å skiriamosios gebos BpuJI N-domeno/DNR komplekso erdvinė struktūrą, paaiškėjo, kad šį domeną sudaro du „sparnuotą“ spiralė-linkis-spiralė motyvą turintys subdomenai. BpuJI taikinį atpažįsta aminorūgštys, esančios N-rankoje ir abiejų spiralė-linkis-spiralė motyvų atpažinimo spiralėse. BpuJI N-domenas yra labiausiai panašus į Nt.BspD6I nukleazę, kerpančią vieną DNR grandinę. Nt.BspD6I/DNR komplekso struktūros modelis rodo, kad Nt.BspD6I ir BpuJI taikinį atpažįstantys struktūriniai elementai yra panašūs.

Mutacijos, atsiradusios atitinkamuose žmogaus genuose, gali lemti pakitusių baltymų atsiradimą, kurie sukelia įvairias ligas (pvz.: vėžį), klaidingą embriono vystymąsi ar priešlaikinę mirtį. Tokios genetinės ligos gali būti gydomos genų terapijos būdu. Labiausiai vystoma genų terapijos strategija yra paremta homologine rekombinacija, kurios metu DNR seka, naudojama geno taisymui, yra patiekiama in trans. Natūraliai žinduolių ląstelėse homologinė rekombinacija (HR) vyksta žemu rekombinacijos dažniu (10-6). Tačiau yra žinoma, kad dvigrandininio trūkio įvedimas žymiai pagreitina HR (10-1). In vivo eksperimentų atveju dvigrandininio trūkio įvedimas turi būti ypač tikslus, todėl šis metodas reikalauja naujų molekulinių įrankių, kurie būtų itin specifiški ir griežtai kontroliuojami. Šiame darbe mes orientavomės į itin specifiškų ir griežtai kontroliuojamų meganukleazių kūrimą naudojant restrikcijos endonukleazių (REazių)-tripleksą formuojančių oligonukleotidų (TFO) konjugatus. REazių-TFO konjugatuose TFO suteikia specifiškumą prailgintam atpažinimo taikiniui per DNR triplekso susidarymą taip nukreipdamas restrikcijos fermentą prie konkretaus taikinio kur norima įvesti dvigrandininį trūkį. Šiuo tyrimu mes parodėme dvi alternatyvias restrikcijos endonukleazių-TFO konjugatų aktyvumo reguliavimo strategijas, kas leistų šias nukleazes panaudoti in vivo tyrimuose. Tuo tikslu buvo pasirinkti ortodoksiniai restrikcijos fermentai MunI ir Bse634I, kurie mūsų laboratorijoje yra gerai... [toliau žr. visą tekstą] / Simple mutations within the coding region of critical human genes can lead to the formation of abnormal proteins, resulting in various diseases (e.g. cancer), in failure of an embryo to develop, or premature death. Genetic diseases can only be truly cured via restoration of defective gene function and one of the most promising strategies is based on homologous recombination. Naturally homologous recombination occurs with a low frequency (1 in 106 transfected cells), however it is known that DNA double-strand breaks enhance the efficiency of homologous recombination by several orders of magnitude (up to 10,000-fold). Therefore, gene therapy via homologous recombination requires new molecular tools that should be highly specific and rigorously controllable. In this work we have focused on the development of restriction enzyme-triple helix forming oligonucleotide (TFO) conjugates, where TFO provides specificity for the extended recognition site through the triple helix formation and addresses restriction enzyme to a particular target site where it introduces a double stranded break. We provide proof-of-concept demonstrations of two alternative strategies to control the DNA cleavage activity of restriction endonuclease-TFO conjugates, that allows adopt them in in vivo experiments. To this end we used restriction endonucleases MunI and Bse634I, which were structurally and biochemically characterized before in our laboratory. We successfully combined the restriction endonuclease... [to full text]

Simple mutations within the coding region of critical human genes can lead to the formation of abnormal proteins, resulting in various diseases (e.g. cancer), in failure of an embryo to develop, or premature death. Genetic diseases can only be truly cured via restoration of defective gene function and one of the most promising strategies is based on homologous recombination. Naturally homologous recombination occurs with a low frequency (1 in 106 transfected cells), however it is known that DNA double-strand breaks enhance the efficiency of homologous recombination by several orders of magnitude (up to 10,000-fold). Therefore, gene therapy via homologous recombination requires new molecular tools that should be highly specific and rigorously controllable. In this work we have focused on the development of restriction enzyme-triple helix forming oligonucleotide (TFO) conjugates, where TFO provides specificity for the extended recognition site through the triple helix formation and addresses restriction enzyme to a particular target site where it introduces a double stranded break. We provide proof-of-concept demonstrations of two alternative strategies to control the DNA cleavage activity of restriction endonuclease-TFO conjugates, that allows adopt them in in vivo experiments. To this end we used restriction endonucleases MunI and Bse634I, which were structurally and biochemically characterized before in our laboratory. We successfully combined the restriction endonuclease... [to full text] / Mutacijos, atsiradusios atitinkamuose žmogaus genuose, gali lemti pakitusių baltymų atsiradimą, kurie sukelia įvairias ligas (pvz.: vėžį), klaidingą embriono vystymąsi ar priešlaikinę mirtį. Tokios genetinės ligos gali būti gydomos genų terapijos būdu. Labiausiai vystoma genų terapijos strategija yra paremta homologine rekombinacija, kurios metu DNR seka, naudojama geno taisymui, yra patiekiama in trans. Natūraliai žinduolių ląstelėse homologinė rekombinacija (HR) vyksta žemu rekombinacijos dažniu (10-6). Tačiau yra žinoma, kad dvigrandininio trūkio įvedimas žymiai pagreitina HR (10-1). In vivo eksperimentų atveju dvigrandininio trūkio įvedimas turi būti ypač tikslus, todėl šis metodas reikalauja naujų molekulinių įrankių, kurie būtų itin specifiški ir griežtai kontroliuojami. Šiame darbe mes orientavomės į itin specifiškų ir griežtai kontroliuojamų meganukleazių kūrimą naudojant restrikcijos endonukleazių (REazių)-tripleksą formuojančių oligonukleotidų (TFO) konjugatus. REazių-TFO konjugatuose TFO suteikia specifiškumą prailgintam atpažinimo taikiniui per DNR triplekso susidarymą taip nukreipdamas restrikcijos fermentą prie konkretaus taikinio kur norima įvesti dvigrandininį trūkį. Šiuo tyrimu mes parodėme dvi alternatyvias restrikcijos endonukleazių-TFO konjugatų aktyvumo reguliavimo strategijas, kas leistų šias nukleazes panaudoti in vivo tyrimuose. Tuo tikslu buvo pasirinkti ortodoksiniai restrikcijos fermentai MunI ir Bse634I, kurie mūsų laboratorijoje yra gerai... [toliau žr. visą tekstą]

Semester project deals with the processing of data from TEM and their analysis (to- mography, single particle analysis). The main aim of this work is to determine the 3D structure of the studied enzyme. As a test sample with low symmetry is used restriction endonuclease EcoR124I.

<div> <div> <div> <p>Prokaryotic Argonautes (pAgos) have been proposed as more flexible tools for gene- editing as they do not require sequence motifs adjacent to their targets for function. One promising pAgo candidate from the halophilic archaeon Natronobacterium gregoryi (NgAgo) has been the subject of intense debate regarding its potential in eukaryotic systems. NgAgo was initially claimed to edit genes in mammalian cells, but the report was retracted due to replication failure. Due to low solubility, subsequent studies refolded NgAgo and suggested that it cuts RNA but not DNA; however, mutation of the conserved active site does not abolish cleavage activity, raising the possibility of nuclease contamination. Another independent study demonstrated gene-editing via NgAgo in bacteria. These inconsistent results underscore the knowledge gap and roadblock for NgAgo-based gene-editing tool development. <br><br> </p><div> <div> <div> <p>In this work, I revisit this enzyme and characterize its function in vitro and in a bacterial system. The halophilic features of NgAgo have been neglected in the literature, leading to inconclusive results. Like other halophilic proteins, NgAgo has modified amino acid composition, leading to failure of domain identification/function prediction via sequence alignment. Indeed, using more sensitive structural alignments, I identified a new single-stranded DNA binding domain, repA, in NgAgo and other halophilic pAgos. Due to its halophilic nature, NgAgo expresses poorly in low-salt environments, with the majority of protein being insoluble and inactive even after refolding. However, soluble NgAgo indeed cuts DNA. NgAgo DNA-cleaving activity can only be abolished via mutation in the canonical PIWI domain and repA deletion, revealing a new catalytic behavior in pAgos. Moreover, NgAgo requires both repA and PIWI domains to create double- stranded DNA breaks, leading to cell death or enhancing homologous recombination, or gene- editing, at a modest level in bacteria. Rational protein engineering of NgAgo was also pursued to increase solubility. Although three out of seven mutants showed significant increases in solubility, they lost the ability to cleave DNA in E.coli. Structural modeling revealed some subtle but important differences in the protein structures, explaining why the mutants lose their function. Besides, a selection system for improving endonuclease activity was optimized for future pAgo optimization. Collectively, this work revealed that NgAgo possesses unique catalytic behavior in the pAgo family and has some gene-editing application potential. More importantly, this work expands knowledge of the pAgo family, providing a foundation for future pAgo-based gene- editing tool development. </p> </div> </div> </div> </div> </div> </div>

Indiana University-Purdue University Indianapolis (IUPUI) / Pancreatic ductal adenocarcinoma (PDAC) is an extremely deadly disease characterized by aggressive metastasis and therapeutic resistance. Reactive stroma in pancreatic tumors contributes to tumor signaling, fibrosis, inflammation, and hypoxia. Hypoxia signaling creates a more aggressive phenotype with increased potential for metastasis and decreased therapeutic efficacy. Carbonic anhydrase IX (CA9) functions as part of the cellular response to hypoxia by regulating intracellular pH to promote cell survival. Apurinic/Apyrimidinic Endonuclease-1-Reduction/oxidation Effector Factor 1 (APE1/Ref-1) is a multi-functional protein with two major activities: endonuclease activity in DNA base excision repair and a redox signaling activity that reduces oxidized transcription factors, enabling them to bind target sequences in DNA. APE1/Ref-1 is a central node in redox signaling, contributing to the activation of transcription factors involved in tumor survival, growth, and hypoxia signaling. This work evaluates the mechanisms underlying PDAC cell responses to hypoxia and APE1/Ref-1 redox signaling control of hypoxia inducible factor 1 alpha (HIF1a), a critical factor in hypoxia-induced CA9 transcription. We hypothesized that obstructing the HIF-CA9 axis at two points via APE1/Ref-1 inhibition and CA9 inhibition results in enhanced PDAC cell killing under hypoxic conditions. We found that HIF1a-mediated induction of CA9 is significantly attenuated following APE1/Ref-1 knock-down or redox signaling inhibition in patient-derived PDAC cells and pancreatic cancer-associated fibroblast cells. Additionally, dual-targeting of APE1/Ref-1 redox signaling activity and CA9 activity results in enhanced acidification and cytotoxicity of PDAC cells under hypoxic conditions as well as decreased tumor growth in an ex-vivo 3-dimensional tumor co-culture model. Further experiments characterized novel analogs of clinically relevant drugs targeting the key enzymes in this pathway, resulting in improved potency. These results underscore the notion that combination therapy is essential and demonstrate the potential clinical utility of blocking APE1/Ref-1 and CA9 function for novel PDAC therapeutic treatment.

No description available.

DNA needs to be accurately copied during DNA replication for a normal cell function. Errors during DNA replication can cause genomic instability that can lead to cancer. To avoid mistakes during the process of DNA replication, nuclease enzymes can act as molecular scissors in removing lethal DNA structures. Therefore, Flap endonuclease 1 (FEN1) is an enzyme that can cleave the 5’flap primer during Okazaki fragment maturation. However, studies have shown that overexpression of FEN1 is associated with different types of cancer. Thus, targeting FEN1 represents a potential for enhancing cancer therapy. However, structural investigation of FEN1 and factors that influence DNA binding need to be comprehensively studied at the molecular level before designing an inhibitor. Thus, this thesis aimed to investigate and compare the catalytic behavior of FEN1wt, FEN1K93A, and FEN1D181A in different experimental conditions. We have found that the activity of FEN1 is affected by the presence of divalent metal ions such as Ca2+ and Mg2+ by performing enzymatic assays. Using the microscale thermophoresis technique, we determined the dissociation constants for FEN1 proteins. Additionally, we performed a thermal shift assay in different conditions which gave us additional insights into the stability of the protein-DNA complex in FEN1. We have found that protein-DNA complex in FEN1D181 is more stable than FEN1wt and FEN1K93A by having a higher melting temperature. Lastly, I used the NMR technique to map the conformational changes within FEN1 proteins upon interacting with divalent metal ions such as Mg2+ ions. To do this, I performed a series of Mg2+ ions titration for FEN1 (WT, K93A, and D181A) using a 2D 1 H 15N TROSY-HSQC experiment to monitor the chemical shifts changes to the chemical environment around the N-H backbone amides of the protein. We have found that both WT and K93A FEN1 proteins interact in a similar way with Mg2+ ions, i.e., explicitly targeting first the higher affinity catalytic site, then spreading around several unspecific low-affinity sites across the protein; however, we observed only the unspecific and weak milli molar binding affinity in FEN1D181A across the entire protein surface upon interacting with Mg2+ ions.

No description available.