PCNA est une protéine essentielle qui intervient dans de nombreux mécanismes cellulaires et qui possède de nombreuses modifications post-traductionnelles (MPTs) dont les fonctions de certaines, restent encore inconnues. Afin d’étudier la fonction de ces MPTs, nous avons développé un nouvel outil génétique permettant in cellulo, de substituer la protéine endogène PCNA par une version mutée de la protéine appelée version de complémentation. La technique consiste à cotransfecter des cellules en culture avec deux types de plasmides. Un premier plasmide permet l’invalidation du gène de PCNA endogène dans les cellules transfectées par le système CRISPR-Cas9. Le deuxième plasmide dit de complémentation permet l’expression d’une forme mutée de PCNA. Sur l’ensemble d’une banque de mutants testés, deux mutants de PCNA se sont avérés être létaux (D122A et E124A). Nous avons démontré que ces deux sites sont impliqués dans l’initiation d’une voie de dégradation ubiquitine dépendante CRL4Cdt2 essentielle pour la mise en place de la protéolyse d’un cocktail de protéines (cdt1, p21, set8) durant la phase S. Nous avons démontré que les cellules mutantes pour PCNA (D122A et E124A) accumulent la protéine p21. Ce défaut de dégradation de p21 provoque alors des évènements de re-réplication menant à terme à la mort des cellules mutantes. / PCNA is an essential protein that is involved in many cellular mechanisms and has many post-translational modifications (PTMs). The functions of some PTMs, still remain unknown. In order to study the function of these PTMs, we have developed a new genetic tool allowing, in cellulo, the substitution of endogenous PCNA protein with a mutated version of the protein named complementation version. The technique involves cotransfection of the cells in culture with two types of plasmids. A first plasmid allows invalidation of the endogenous PCNA gene in transfected cells by the CRISPR-Cas9 system. The second plasmid, named complementation plasmid allows the expression of a mutated form of PCNA. In the whole bank of tested mutants, two PCNA mutants were found to be lethal (D122A and E124A). We have demonstrated that these two sites are involved in the initiation of an ubiquitin-dependent protein degradation CRL4Cdt2 pathway essential for the proteolysis of a protein cocktail (cdt1, p21, set8) during the S phase. We demonstrated that PCNA mutant cells (D122A and E124A) accumulate p21 protein. This lack of degradation of p21 then causes re-replication events leading ultimately to the mutant cells death.

Obesity increases the risk of colon cancer as well as the expression of many cancer markers, ostensibly due to the interaction between insulin resistance and adipocyte production of hormones, mitogens and cytokines which collaborate to enhance proliferation signaling and impair the DNA damage response. Cdc7 and PCNA are both proteins involved in the DNA damage response as well as DNA replication. Both have also been shown to be upregulated in human tumours. To assess Cdc7 and PCNA roles during the DNA damage response in obese and lean animals, we administered azoxymethane (AOM), a colon-specific carcinogen, to obese and lean rats. Cdc7 and PCNA levels in colonic mucosal protein extracts from obese Zucker rats were compared with those from their lean counterparts. Significant differences were seen between lean and obese animals 3 hours post-AOM (lean Cdc7 levels > obese Cdc7 levels) and 24 hours post-AOM (lean PCNA levels > obese PCNA levels). This result suggests an impaired checkpoint response in obese animals relative to lean animals and supports a previously reported early role for Cdc7 in the checkpoint signaling cascade relative to a later role of PCNA in DNA damage repair. At the time tumours appeared (32 weeks post-AOM), colonic mucosal Cdc7 levels of obese rats exceeded that of their lean counterparts, suggesting that the obese metabolic environment causes upregulation of Cdc7 in obese rat epithelia. Cdc7 and PCNA levels were then compared between tumours and mucosa in obese and Sprague Dawley rats. Tumour Cdc7 levels were upregulated relative to mucosal levels in more samples than tumour PCNA levels, suggesting Cdc7 may be a more sensitive tumour marker. No significant differences in Cdc7 levels were seen between obese tumours and mucosa, likely due to elevation of obese mucosal Cdc7 levels. However, Sprague Dawley (non-obese) rats showed significantly higher Cdc7 and PCNA levels in tumours than mucosa, consistent with previous studies in human tissues. These results suggest that Cdc7 may be a more sensitive tumour marker than PCNA, but that its utility as a biomarker of colon cancer is dependent on the metabolic state (leanness) of the individual.

Obesity increases the risk of colon cancer as well as the expression of many cancer markers, ostensibly due to the interaction between insulin resistance and adipocyte production of hormones, mitogens and cytokines which collaborate to enhance proliferation signaling and impair the DNA damage response. Cdc7 and PCNA are both proteins involved in the DNA damage response as well as DNA replication. Both have also been shown to be upregulated in human tumours. To assess Cdc7 and PCNA roles during the DNA damage response in obese and lean animals, we administered azoxymethane (AOM), a colon-specific carcinogen, to obese and lean rats. Cdc7 and PCNA levels in colonic mucosal protein extracts from obese Zucker rats were compared with those from their lean counterparts. Significant differences were seen between lean and obese animals 3 hours post-AOM (lean Cdc7 levels > obese Cdc7 levels) and 24 hours post-AOM (lean PCNA levels > obese PCNA levels). This result suggests an impaired checkpoint response in obese animals relative to lean animals and supports a previously reported early role for Cdc7 in the checkpoint signaling cascade relative to a later role of PCNA in DNA damage repair. At the time tumours appeared (32 weeks post-AOM), colonic mucosal Cdc7 levels of obese rats exceeded that of their lean counterparts, suggesting that the obese metabolic environment causes upregulation of Cdc7 in obese rat epithelia. Cdc7 and PCNA levels were then compared between tumours and mucosa in obese and Sprague Dawley rats. Tumour Cdc7 levels were upregulated relative to mucosal levels in more samples than tumour PCNA levels, suggesting Cdc7 may be a more sensitive tumour marker. No significant differences in Cdc7 levels were seen between obese tumours and mucosa, likely due to elevation of obese mucosal Cdc7 levels. However, Sprague Dawley (non-obese) rats showed significantly higher Cdc7 and PCNA levels in tumours than mucosa, consistent with previous studies in human tissues. These results suggest that Cdc7 may be a more sensitive tumour marker than PCNA, but that its utility as a biomarker of colon cancer is dependent on the metabolic state (leanness) of the individual.

名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成7年3月27日 金子健一朗氏の博士論文として提出された

PCNA and RPA are required for DNA mismatch repair (MMR), but their rolesin the pathway are not fully understood. Using an affinity pull-down approach, weshow that (1) increased PCNA binding to DNA heteroduplexes is associated withthe appearance and accumulation of excision products; and (2) RPAphosphorylation occurs when DNA polymerase ?? binds to the DNA substrate. Wetherefore hypothesize that PCNA plays an important role in mismatch-provokedexcision and that RPA phosphorylation plays an important role in DNA resynthesis.To determine the role of PCNA in MMR, mismatch-provoked and nick-directedexcision was assayed in a cell-free system in the presence of the PCNA inhibitor,p21CIP1/WAF. We show that whereas PCNA is essential for 3' directed excision, it isdispensable for the 5' directed reaction, suggesting a differential role for PCNA inMMR. We further find that the PCNA-dependent pathway is the only pathway for3' directed excision, but there are at least two pathways for 5' directed excision,one of which is a PCNA-independent 5' excision pathway. To determine if RPAphosphorylation facilitates DNA resynthesis, a gap-filling assay was developedusing both a cell-free system and a purified system, and we demonstrate that RPAphosphorylation stimulates DNA polymerase ??-catalyzed resynthesis in bothsystems. Kinetic studies indicate that phosphorylated RPA has a lower affinity forDNA compared with un-phosphorylated RPA. Therefore, the stimulation ofresynthesis by phosphorylated RPA is likely due to the fact that phosphorylationpromotes the release of RPA from DNA, thereby making DNA template availablefor resynthesis.

O propósito do presente estudo foi analisar as células epiteliais odontogênicas procurando um entendimento maior sobre a natureza e conseqüentemente o comportamento de algumas lesões odontogênicas. A expressão imunoistoquímica de p53 e PCNA foi analisada em cisto radicular, cisto dentígero, ceratocisto odontogênico e cisto odontogênico calcificante (Cisto de Gorlin) onde verificou-se que no cisto radicular e cisto dentígero a expressão dos marcadores está relacionado com proliferação e stress celular causado pelo estímulo inflamatório e em ceratocisto odontogênico e Cisto de Gorlin a expressão dos marcadores corresponde a proliferação celular não descartando também a presença de mutação no gene TP53. Também foi observada a expressão de Ki-67, EGFR e Survivin em folículo pericoronário, ceratocisto odontogênico e cisto dentígero que mostrou que as células epiteliais dos folículos pericoronários têm potencial proliferativo para formar lesões odontogênicas e que a proliferação das células do cisto dentígero é relacionada com o estímulo inflamatório. Todos os marcadores estudados comprovaram a natureza neoplásica do ceratocisto odontogênico. / The purpose of this study was to analyze odontogenic epithelial cells to contribute to the knowledge about their nature and, consequently, about the behavior of certain odontogenic lesions. Immunohistochemical expressions of p53 and PCNA were analyzed in radicular cysts, dentigerous cysts, odontogenic keratocysts and calcifying odontogenic cysts (Gorlin cyst). In radicular and dentigerous cysts, the expression of these markers was associated with cell proliferation and stress caused by an inflammatory stimulus. In keratocysts and Gorlin cysts, the expression of markers corresponded to cell proliferation. Results also showed possible mutation in TP53 gene. Also, Ki-67, EGFR and Survivin were expressed in pericoronal follicles, odontogenic keratocysts and dentigerous cysts, which demonstrated that epithelial cells of pericoronal follicles may proliferate to form odontogenic lesions and that cell proliferation in dentigerous cysts was associated with an inflammatory stimulus. The analysis of all markers under study confirmed the neoplastic nature of odontogenic keratocysts.

O propósito do presente estudo foi analisar as células epiteliais odontogênicas procurando um entendimento maior sobre a natureza e conseqüentemente o comportamento de algumas lesões odontogênicas. A expressão imunoistoquímica de p53 e PCNA foi analisada em cisto radicular, cisto dentígero, ceratocisto odontogênico e cisto odontogênico calcificante (Cisto de Gorlin) onde verificou-se que no cisto radicular e cisto dentígero a expressão dos marcadores está relacionado com proliferação e stress celular causado pelo estímulo inflamatório e em ceratocisto odontogênico e Cisto de Gorlin a expressão dos marcadores corresponde a proliferação celular não descartando também a presença de mutação no gene TP53. Também foi observada a expressão de Ki-67, EGFR e Survivin em folículo pericoronário, ceratocisto odontogênico e cisto dentígero que mostrou que as células epiteliais dos folículos pericoronários têm potencial proliferativo para formar lesões odontogênicas e que a proliferação das células do cisto dentígero é relacionada com o estímulo inflamatório. Todos os marcadores estudados comprovaram a natureza neoplásica do ceratocisto odontogênico. / The purpose of this study was to analyze odontogenic epithelial cells to contribute to the knowledge about their nature and, consequently, about the behavior of certain odontogenic lesions. Immunohistochemical expressions of p53 and PCNA were analyzed in radicular cysts, dentigerous cysts, odontogenic keratocysts and calcifying odontogenic cysts (Gorlin cyst). In radicular and dentigerous cysts, the expression of these markers was associated with cell proliferation and stress caused by an inflammatory stimulus. In keratocysts and Gorlin cysts, the expression of markers corresponded to cell proliferation. Results also showed possible mutation in TP53 gene. Also, Ki-67, EGFR and Survivin were expressed in pericoronal follicles, odontogenic keratocysts and dentigerous cysts, which demonstrated that epithelial cells of pericoronal follicles may proliferate to form odontogenic lesions and that cell proliferation in dentigerous cysts was associated with an inflammatory stimulus. The analysis of all markers under study confirmed the neoplastic nature of odontogenic keratocysts.

abstract: Biophysical techniques have been increasingly applied toward answering biological questions with more precision. Here, three different biological systems were studied with the goal of understanding their dynamic differences, either conformational dynamics within the system or oligomerization dynamics between monomers. With Cy3 on the 5' end of DNA, the effects of changing the terminal base pair were explored using temperature-dependent quantum yields. It was discovered, in combination with simulations, that a terminal thymine base has the weakest stacking interactions with the Cy3 dye compared to the other three bases. With ME1 heterodimers, the goal was to see if engineering a salt bridge at the dimerization interface could allow for control over dimerization in a pH-dependent manner. This was performed experimentally by measuring FRET between monomers containing either a Dap or an Asp mutation and comparing FRET efficiency at different pHs. It was demonstrated that the heterodimeric salt bridge would only form in a pH range near neutrality. Finally, with DNA processivity clamps, one aim was to compare the equilibrium dissociation constants, kinetic rate constants, and lifetimes of the closed rings for beta clamp and PCNA. This was done using a variety of biophysical techniques but with three as the main focus: fluorescence correlation spectroscopy, single-molecule experiments, and time-correlated single photon counting measurements. The stability of beta clamp was found to be three orders of magnitude higher when measuring solution stability but only one order of magnitude higher when measuring intrinsic stability, which is a result of salt bridge interactions in the interface of beta clamp. Ongoing work built upon the findings from this project by attempting to disrupt interface stability of different beta clamp mutants by adding salt or changing the pH of the solution. Lingering questions about the dynamics of different areas of the clamps has led to another project for which we have developed a control to demystify some unexpected similarities between beta clamp mutants. With that project, we show that single-labeled and double-labeled samples have similar autocorrelation decays in florescence correlation spectroscopy, allowing us to rule out the dyes themselves as causing fluctuations in the 10-100 microsecond timescale. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

O propósito do presente estudo foi analisar as células epiteliais odontogênicas procurando um entendimento maior sobre a natureza e conseqüentemente o comportamento de algumas lesões odontogênicas. A expressão imunoistoquímica de p53 e PCNA foi analisada em cisto radicular, cisto dentígero, ceratocisto odontogênico e cisto odontogênico calcificante (Cisto de Gorlin) onde verificou-se que no cisto radicular e cisto dentígero a expressão dos marcadores está relacionado com proliferação e stress celular causado pelo estímulo inflamatório e em ceratocisto odontogênico e Cisto de Gorlin a expressão dos marcadores corresponde a proliferação celular não descartando também a presença de mutação no gene TP53. Também foi observada a expressão de Ki-67, EGFR e Survivin em folículo pericoronário, ceratocisto odontogênico e cisto dentígero que mostrou que as células epiteliais dos folículos pericoronários têm potencial proliferativo para formar lesões odontogênicas e que a proliferação das células do cisto dentígero é relacionada com o estímulo inflamatório. Todos os marcadores estudados comprovaram a natureza neoplásica do ceratocisto odontogênico. / The purpose of this study was to analyze odontogenic epithelial cells to contribute to the knowledge about their nature and, consequently, about the behavior of certain odontogenic lesions. Immunohistochemical expressions of p53 and PCNA were analyzed in radicular cysts, dentigerous cysts, odontogenic keratocysts and calcifying odontogenic cysts (Gorlin cyst). In radicular and dentigerous cysts, the expression of these markers was associated with cell proliferation and stress caused by an inflammatory stimulus. In keratocysts and Gorlin cysts, the expression of markers corresponded to cell proliferation. Results also showed possible mutation in TP53 gene. Also, Ki-67, EGFR and Survivin were expressed in pericoronal follicles, odontogenic keratocysts and dentigerous cysts, which demonstrated that epithelial cells of pericoronal follicles may proliferate to form odontogenic lesions and that cell proliferation in dentigerous cysts was associated with an inflammatory stimulus. The analysis of all markers under study confirmed the neoplastic nature of odontogenic keratocysts.

We have previously shown that the insulin-like growth factor 1 receptor (IGF-1R) translocates to the cell nucleus, where it binds to enhancer-like regions and increases gene transcription. Further studies have demonstrated that nuclear IGF-1R (nIGF-1R) physically and functionally interacts with some nuclear proteins, i.e. the lymphoid enhancer-binding factor 1 (Lef1), histone H3, and Brahma-related gene-1 proteins. In this study, we identified the proliferating cell nuclear antigen (PCNA) as a nIGF-1R-binding partner. PCNA is a pivotal component of the replication fork machinery and a main regulator of the DNA damage tolerance (DDT) pathway. We found that IGF-1R interacts with and phosphorylates PCNA in human embryonic stem cells and other cell lines. In vitro MS analysis of PCNA co-incubated with the IGF-1R kinase indicated tyrosine residues 60, 133, and 250 in PCNA as IGF-1R targets, and PCNA phosphorylation was followed by mono- and polyubiquitination. Co-immunoprecipitation experiments suggested that these ubiquitination events may be mediated by DDT-dependent E2/E3 ligases (e.g. RAD18 and SHPRH/HLTF). Absence of IGF-1R or mutation of Tyr-60, Tyr-133, or Tyr-250 in PCNA abrogated its ubiquitination. Unlike in cells expressing IGF-1R, externally induced DNA damage in IGF-1R-negative cells caused G(1) cell cycle arrest and S phase fork stalling. Taken together, our results suggest a role of IGF-1R in DDT.