Assim como o número de casos de câncer vem aumentando em nível global, a busca por abordagens terapêuticas visando uma maior eficácia com um menor poder de causar efeitos prejudiciais aos pacientes também vem crescendo. As antraciclinas e antracenodionas, as quais tem como exemplos, doxorrubicina (DOX) e mitoxantrona (MTX), respectivamente, são fármacos utilizados na quimioterapia em diversas neoplasias incluindo tumores sólidos e não sólidos tais como de mama, leucemias, linfomas, sarcomas etc. Embora sejam eficazes ao que se propõem, o tratamento com estas moléculas pode acarretar em efeitos secundários, tais como arritmias e insuficiência cardíaca. Estas drogas além de interagirem com o ferro e apresentarem capacidade de gerar espécies reativas de oxigénio (ROS), apresentam como principal mecanismo a inibição da enzima topoisomerase 2 (Top2). Os inibidores de PARP-1 emergiram como uma nova alternativa para tratar determinados tipos de neoplasias em que a letalidade sintética possa ser explorada. Além disto, já foi relatado que a toxicidade cardíaca induzida por DOX seja influenciada pela atividade de PARP-1. O objetivo desta tese foi, portanto, avaliar a influência da inibição de PARP-1 na toxicidade cardíaca de DOX e MTX em células cardíacas. Células foram incubadas durante 24h com DOX ou MTX na presença ou na ausência de inibidor de PARP-1. Ensaios de viabilidade, apoptose e genotoxicidade e foram realizados. Além disso, a fosforilação de proteínas envolvidas na resposta a danos no DNA (ATM, MRE-11 e H2AX) foram avaliadas por western blot e imunofluorescência. Os resultados demonstraram que a inibição de PARP-1, apesar de diminuir a concentração de ROS, diminui a viabilidade de células H9c2 tratadas com DOX ou MTX por aumentar a geração de quebras duplas no DNA induzida por estes fármacos. / As the number of people with cancer are globally increasing, the search for therapeutic approaches that increases efficiency decreasing harmful effects to patients is also growing, giving rise to cardio-oncology. Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. PARP-1 inhibitors have emerged as a new alternative for treating certain types of malignancies in which the synthetic lethality can be exploited. Furthermore, it has been reported that DOX-induced cardiac cardiotoxicity is influenced by PARP-1 activity. The main goal of this thesis was, therefore, to evaluate PARP-1 inhibition influence in cardiac toxicity of DOX and MTX in cardiac cells. Cells were incubated for 24h with MTX or DOX in presence or absence of PARP-1 inhibitor. Viability, oxidative stress and genotoxicity assays have been conducted. Furthermore, phosphorylation of proteins involved in response to DNA damage (ATM, H2AX and MRE-11) were evaluated by western blot and immunofluorescence. Results demonstrated that inhibition of PARP-1, although decreasing ROS generation, decreases H9c2 cells viability after DOX or MTX by increasing DNA double strand break generation induced by these drugs.

Assim como o número de casos de câncer vem aumentando em nível global, a busca por abordagens terapêuticas visando uma maior eficácia com um menor poder de causar efeitos prejudiciais aos pacientes também vem crescendo. As antraciclinas e antracenodionas, as quais tem como exemplos, doxorrubicina (DOX) e mitoxantrona (MTX), respectivamente, são fármacos utilizados na quimioterapia em diversas neoplasias incluindo tumores sólidos e não sólidos tais como de mama, leucemias, linfomas, sarcomas etc. Embora sejam eficazes ao que se propõem, o tratamento com estas moléculas pode acarretar em efeitos secundários, tais como arritmias e insuficiência cardíaca. Estas drogas além de interagirem com o ferro e apresentarem capacidade de gerar espécies reativas de oxigénio (ROS), apresentam como principal mecanismo a inibição da enzima topoisomerase 2 (Top2). Os inibidores de PARP-1 emergiram como uma nova alternativa para tratar determinados tipos de neoplasias em que a letalidade sintética possa ser explorada. Além disto, já foi relatado que a toxicidade cardíaca induzida por DOX seja influenciada pela atividade de PARP-1. O objetivo desta tese foi, portanto, avaliar a influência da inibição de PARP-1 na toxicidade cardíaca de DOX e MTX em células cardíacas. Células foram incubadas durante 24h com DOX ou MTX na presença ou na ausência de inibidor de PARP-1. Ensaios de viabilidade, apoptose e genotoxicidade e foram realizados. Além disso, a fosforilação de proteínas envolvidas na resposta a danos no DNA (ATM, MRE-11 e H2AX) foram avaliadas por western blot e imunofluorescência. Os resultados demonstraram que a inibição de PARP-1, apesar de diminuir a concentração de ROS, diminui a viabilidade de células H9c2 tratadas com DOX ou MTX por aumentar a geração de quebras duplas no DNA induzida por estes fármacos. / As the number of people with cancer are globally increasing, the search for therapeutic approaches that increases efficiency decreasing harmful effects to patients is also growing, giving rise to cardio-oncology. Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. PARP-1 inhibitors have emerged as a new alternative for treating certain types of malignancies in which the synthetic lethality can be exploited. Furthermore, it has been reported that DOX-induced cardiac cardiotoxicity is influenced by PARP-1 activity. The main goal of this thesis was, therefore, to evaluate PARP-1 inhibition influence in cardiac toxicity of DOX and MTX in cardiac cells. Cells were incubated for 24h with MTX or DOX in presence or absence of PARP-1 inhibitor. Viability, oxidative stress and genotoxicity assays have been conducted. Furthermore, phosphorylation of proteins involved in response to DNA damage (ATM, H2AX and MRE-11) were evaluated by western blot and immunofluorescence. Results demonstrated that inhibition of PARP-1, although decreasing ROS generation, decreases H9c2 cells viability after DOX or MTX by increasing DNA double strand break generation induced by these drugs.

Poly(ADP-ribose)polymerase-1 and -2 (PARP1/2) are nuclear proteins involved in DNA repair. Tumors with defects in homologous recombination, including BRCA1- and BRCA2-deficient cancers, have been shown to be sensitive to PARP inhibition. The Weissleder group has synthesized fluorescent and radioactive derivatives of the PARP1/2 inhibitor AZD2281. We hypothesized that fluorescent and radioactive AZD2281-based imaging agents would quantify PARP1/2 expression in vitro and in vivo. To test this hypothesis, a panel of pancreatic ductal adenocarcinoma and ovarian carcinoma cell lines were characterized by immunocytochemistry for PARP1/2 expression. AZD2281-derived fluorescence signal correlated with anti-PARP antibody fluorescence signal strength in vitro. Four cell lines representing a range of PARP1/2 expression levels were then xenografted into Nu/Nu mice. Mice bearing four tumor types each were imaged with AZD2281-derived imaging agents, sacrificed, and their tumors excised for stand-alone imaging and Western blot. AZD2281-derived signal correlated with tumor PARP1/2 expression determined by Western blot, indicating that PARP1/2 expression level is a determinant of fluorescent signal strength and SUVs of AZD2281-derived agents in vivo. These data indicate that AZD2281-derived agents are useful tools for quantifying intracellular PARP1/2 both in vitro and in vivo, which could one day enable prospective identification of tumors likely to respond to PARP inhibitors.

OBJECTIVE: Despite advancement in targeted therapeutics, women’s cancers remain particularly deadly. The response to Poly (ADP-ribose) Polymerase (PARP) inhibitors, a prominent targeted therapy indicated for use in these cancers, is largely dictated by the cellular status of homologous recombination (HR) and varies among patients possibly due to intrinsic and acquired mechanisms of resistance. A recent effort to identify targetable pathways to enhance toxicity of PARPi identified the Snf2-like chromatin remodeling enzyme, Amplified in Liver Cancer 1 (ALC1), as a key determinant of PARPi sensitivity. While this discovery proposes a link between chromatin re-modeling and PARPi sensitivity, the mechanism underlying the relationship remains unclear. This study aims to validate ALC1 as a determinant of PARPi sensitivity, characterize the phenotype of ALC1 loss, investigate mechanisms of synthetic lethality and identify possibilities for future studies and clinical implementation. METHODS: UWB1.289, SUM149PT, DLD1, U-2 OS, and hTERT-RPE1 cells were cultured and used to validate ALC1-mediated PARPi sensitivity in a variety of viability assays. ALC1 depleted cells were complemented with various functional mutants to assess protein domains that were essential to PARPi-resistance. A Dual CRISPR-Cas9 system was implemented to screen BRCA1 complemented UWB1.289 cells with a sgRNA library targeting a multitude of DNA-repair associated genes in order to assess synthetic lethal/resistant relationships across different DNA-repair pathways. A MNase-sensitivity assay was developed and optimized to assess the global condensation of chromatin with combinational loss of ALC1 and PARP1. The 265-FokI system was employed to quantify the DNA damage response (DDR) to singular induced double strand breaks. Clonogenic assays were used to determine synergy with ionizing radiation. RESULTS: The loss of ALC1 significantly and selectively hypersensitized both BRCA1 and BRCA2-deficient cells to PARPi. In ALC1 depleted cells, the addition of ALC1 cDNA was able to rescue cells from PARPi hypersensitivity while cDNA with mutations in either the macro-domain or ATPase active domain remained sensitive. Screening DNA-repair pathways to assess synergy with PARPi and ALC1 loss in HR-proficient settings revealed that the loss of several HR and Alt-EJ genes selectively re-sensitized cells to PARPi. Interestingly, the loss of BER genes, including several glycosylases, were epistatic or resulted in a protective effect to PARPi. The reduction of NHEJ, NER, MMR or RER did not significantly alter cellular response to PARPi. Further, nucleosome relaxation was significantly inhibited in cells treated with PARPi, ALC1 loss or in combination via MNase assay. The recruitment of repair proteins to DSBs was significantly inhibited by PARPi as assessed by 265-FokI immunofluorescence. The addition of PARPi in the setting of ALC1 loss significantly increased the cytotoxicity of ionizing radiation. Analyzing TCGA data collected from patients’ tumors, ALC1 may be overexpressed in many cancers and alterations in ALC1 may predict patient responses to traditional and targeted cancer therapies. CONCLUSION: Using various models of BRCA1/2 deficiency we were able to validate the ability of ALC1 depletion to hypersensitize HR-deficient cells to PARPi. We provided insight into the mechanisms by which this phenomenon may be taking place, including chromatin compaction and the inhibition of DNA-damage repair. In addition, we provided therapeutic rationale that ALC1 may be targeted with PARP1 in synergy with other DNA-damaging agents. Overall, we believe that ALC1 is a prominent, viable and novel target of inducing PARP inhibitor sensitivity, that may help improve outcomes for patients with PARP inhibitor-resistant HR-deficient cancers. / 2022-06-04T00:00:00Z

No description available.

Fusarium oxysporum is a filamentous fungus that is known to invade over a hundred different hosts and poses a major threat to the economy and food supply world-wide. Poly (Adenosine diphosphate-Ribose) Polymerase (PARP) is a family of regulatory proteins that affect change in the cell through transfer of ADP-Ribose moieties onto target molecules. The most well-studied PARP protein is the human PARP1, a PARylating nuclear protein that serves as our model PARP protein. F. oxysporum was found to contain a large expansion of PARP catalytic-domain-containing proteins compared to other filamentous fungi. We utilized in silico multiple sequence alignments and domain predictions to identify a human PARP1 homolog termed foPARP1 that was conserved within the core chromosomes in all three strains within our comparative system. Our in silico predictions also stated that only one strain, an Arabidopsis pathogen, Fo5176, contained several other predicted catalytically active PARP homologs within the accessory chromosome. To test the effect that foPARP1 knockout would have on DNA damage tolerance, we created a foParp1 knockout and found that only strains Fol4287 and Fo5176 had a significant reduction in tolerance upon being plated with methyl methanesulfonate (MMS), a DNA alkylating agent. To test how global PARylation trends would be affected by foParp1 knockout, we utilized immunodot-blotting with PAR antibodies to assess PARylation in total protein extracts. We found that all strains of the comparative system had the capacity to catalyze the synthesis of long PAR chains, while only Fo47 and Fo5176 had a significant PARylation increase when exposed to MMS, and no samples had a significant increase in PARylation within the foParp1 knockouts. Finally, we utilized RNA-Sequencing to determine the transcriptional impacts that foParp1 knockout would have and found aberrant DNA repair pathways and disruptions in stress responses. Taken together, we conclude that foPARP1 is in fact a functional PARP1 homolog and exhibits similar post-transcriptional modification and transcriptional impacts as its human counterpart. However, we were not able to correlate PARP copy number with DNA stress tolerance, and further research would be needed to assess the full function of the PARP expansion.

No description available.

Le carcinome hépatocellulaire est l'un des cancers les plus fréquents et des plus sévères à travers le monde. Le diagnostic est souvent tardif et les traitements curatifs ne peuvent être proposés qu'à un nombre limité de patients. Les technologies modernes ont permis le développement de nouvelles méthodes de radiothérapie qui montrent aujourd'hui de bons résultats. Par ailleurs, bien que des déficiences dans les voies de réparation de l'ADN soient associées à une instabilité génomique et une susceptibilité au cancer, une inhibition de ces voies sensibilise les cellules cancéreuses à la chimiothérapie et à la radiothérapie. Dans ce contexte, les inhibiteurs de poly(ADP-ribose) polymérases (PARP) ont déjà montré des résultats prometteurs dans des études pré-cliniques et sont en cours d'évaluation clinique pour de nombreux cancers. Ce travail de thèse a consisté en l'évaluation du potentiel des inhibiteurs de PARP en combinaison avec la radiothérapie comme nouvelle option thérapeutique pour le carcinome hépatocellulaire. La première étape de ce travail a été de caractériser les profils d'expression et d'activité de plusieurs membres de la famille PARP dans des cellules cancéreuses du foie et des hépatocytes primaires humains ainsi que dans des tissus hépatiques. En second lieu, nous avons étudié le potentiel de l'inhibiteur de PARP ABT-888 seul et en combinaison à des radiations ionisantes in vitro. Le traitement par l'inhibiteur de PARP ABT-888 en agent seul a montré une sensibilité variable des différentes lignées cellulaires étudiées à cette drogue. Afin de comprendre la sensibilité variable des cellules cancéreuses hépatiques à l'ABT-888, nous avons analysé leur capacité de réparation des dommages à l'ADN et avons observé des capacités différentes entre les lignées cellulaires. Finalement, nous avons pu montrer que l'ABT-888 sensibilise les cellules cancéreuses hépatiques aux radiations ionisantes. Ce travail de recherche a permis de montrer que les inhibiteurs de PARP ont un fort potentiel pour améliorer les méthodes de radiothérapie utilisées dans la prise en charge du carcinome hépatocellulaire / Hepatocellular carcinoma is the third cause of cancer related death. Due its often late diagnosis and advanced stage, a limited number of patients can benefit from curative treatments. There is thus a constant need for new treatment strategies for patients with hepatocellular carcinoma. Targeting DNA repair pathways to sensitize tumor cells to chemoor radiotherapeutic treatments is now a common strategy under investigation for cancer treatment with inhibitors of poly(ADP-ribose) polymerases (PARP) showing great potential. The aim of this work was to evaluate the potential of PARP inhibitors alone and in combination with radiation therapy as a new strategy for the treatment of hepatocellular carcinoma. We first analyzed the expression and activity of different PARP genes in a panel of liver cancer cell lines and primary human hepatocytes as well as their DNA repair capacity and assess the impact of PARP inhibitors alone and in combination with ionizing radiation in these models on cell survival. A large range in expression of PARP family members, PARP activity and sensitivity to ABT-888 in the panel of liver cells was observed as well as differential excision/synthesis repair capacity. Finally, we showed that ABT-888 sensitizes liver cancer cells to the cell killing effects of ionizing radiation. PARP inhibitors show great potential for improving radiation therapy strategies used in the management of hepatocellular carcinoma

L’ADN cellulaire qu’il soit nucléaire ou mitochondrial est constamment soumis à l’action de stress d’origine exogène ou même endogène à la base d’altérations plus ou moins profondes de sa structure. Ces modifications chimiques sont très variées et peuvent aller de l’oxydation d’une base aux cassures double-brins de la molécule d’ADN. Ces dernières sont considérées comme les dommages les plus agressifs pour la cellule car peuvent conduire à la perte d’information et donc à la mort cellulaire. Parmi les systèmes de surveillance de la stabilité du génome figure la Poly(ADP-ribosyl)ation (PARylation). Cette modification post-traductionnelle est assurée essentiellement par les protéines PARP et PARG et est caractérisée par l’incorporation des polymères d’ADP ribose (pADPr) sur des protéines cibles. La PARylation constitue un élément clé dans plusieurs voies de maintien de l’intégrité génomique (BER, NHEJ, HR). La PARylation est aussi décrite au niveau de la mitochondrie mais son rôle dans la gestion des DSBs de l’ADNmt n’est pas connu. Le travail, objet de cette thèse, consiste à étudier le rôle de la PARylation dans le cas des DSB au niveau général chez la drosophile et ensuite de comprendre les mécanismes de gestion des DSB mitochondriales et évaluer l’implication de la PARylation dans ce processus. Nos résultats montrent que : (1) le comportement de la PARylation ne varie pas au cours du processus de cassures et de réparation de l’ADN nucléaire, alors que l’expression des ARNm de PARP-I et PARP-II augmente durant la phase de réparation ; (2) les cassures de l’ADN mitochondrial, induites par la bléomycine, entraînent une augmentation du nombre de copies de l’ADNmt. Cette augmentation transitoire de la quantité de l’ADNmt est observée durant la phase des dommages et retourne à la valeur initiale durant la phase de la réparation. Ce comportement semble être régulé par PARP. L’ensemble de ces résultats suggère que la réparation des DSBs est indépendante de la PARylation au niveau nucléaire mais que la présence de PARP est importante. De plus, PARP semble avoir un rôle dans la régulation de la réplication de l’ADNmt en réponse à un stress génotoxique. / Both nuclear and mitochondrial DNA alterationsarise following exposure to environmental and endogenous stresses. These genomic alterations are various, ranging from base oxidation to DNA strand breaks, single- and double-strand breaks. These damages are highly detrimental to the cell because they can lead to loss of genetic information and thus to cell death. However, cells have developed various mechanisms to counteract this biological issue and to lead up to a complex DNA damage response (DDR). The Poly (ADP- ribosyl) ation (PARylation) is among these DDR systems. This post-translational modification is mainly carried out by PARP and PARG proteins and is characterized by the incorporation of polymers of ADP-ribose on target proteins. The majority of the PARylationfunctions are related to cellular stress response, particulary in response to genomic damages where it is implicated in many DNA integrity pathways such as Base Excision Repair, Non Homologous End Joining and Homologous Recombination. In contrast to the nucleus, PARylation is also described in the mitochondria but its role in mtDNA integrityis still a heavily debate issue, particularly in case of mtDNA DSBs.To understand it, we used Drosophila model wherePARP-B isoform (human PARP-1 ortholog) is the only enzymatically active form in Drosophila PARP family. The aim of this thesis is to study the role of PARylation in response to DSBs induction in nucleus and mitochondrial DNAand then to understand the mechanisms involved in mtDNA integrity and to evaluate the role of PARylation in this process. Our results show that PARylation level remains stable during DSBs induction and also during repair process,contrary to what is shown in Human cells.However, PARP-I and PARP-II mRNA expression increase during repair period. In mitochondria compartment,our data show an increase of mtDNA copy number in presence of mtDNA DSBs. This increased level returns to normal during repair period and seems to be dependent on PARP. All these results suggest that DSBs repair is PARylation independent at the nuclear level but that the presence of PARP is important. In addition, PARP appears to have a role in the regulation of mtDNA replication in response to genotoxic stress.

Made available in DSpace on 2014-12-17T14:03:36Z (GMT). No. of bitstreams: 1 JullianeTAM_TESE_Parcial.pdf: 7138229 bytes, checksum: a06700fccf67cc2db086f62bf86db506 (MD5) Previous issue date: 2014-02-26 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / studies using UV as a source of DNA damage. However, even though unrepaired UV-induced DNA damages are related to mutagenesis, cell death and tumorigenesis, they do not explain phenotypes such as neurodegeneration and internal tumors observed in patients with syndromes like Xeroderma Pigmentosum (XP) and Cockayne Syndrome (CS) that are associated with NER deficiency. Recent evidences point to a role of NER in the repair of 8-oxodG, a typical substrate of Base Excision Repair (BER). Since deficiencies in BER result in genomic instability, neurodegenerative diseases and cancer, it was investigated in this research the impact of XPC deficiency on BER functions in human cells. It was analyzed both the expression and the cellular localization of APE1, OGG1 e PARP-1, the mainly BER enzymes, in different NER-deficient human fibroblasts. The endogenous levels of these enzymes are reduced in XPC deficient cells. Surprisingly, XP-C fibroblasts were more resistant to oxidative agents than the other NER deficient fibroblasts, despite presenting the highest of 8-oxodG. Furthermore, subtle changes in the nuclear and mitochondrial localization of APE1 were detected in XP-C fibroblasts. To confirm the impact of XPC deficiency in the regulation of APE1 and OGG1 expression and activity, we constructed a XPC-complemented cell line. Although the XPC complementation was only partial, we found that XPC-complemented cells presented increased levels of OGG1 than XPC-deficient cells. The extracts from XPC-complemented cells also presented an elevated OGG1 enzimatic activity. However, it was not observed changes in APE1 expression and activity in the XPCcomplemented cells. In addition, we found that full-length APE1 (37 kDa) and OGG1- ? are in the mitochondria of XPC-deficient fibroblasts and XPC-complemented fibroblasts before and after induction of oxidative stress. On the other hand, the expression of APE1 and PARP-1 are not altered in brain and liver of XPC knockout mice. However, XPC deficiency changed the APE1 localization in hypoccampus and hypothalamus. We also observed a physical interaction between XPC and APE1 proteins in human cells. In conclusion, the data suggest that XPC protein has a role in the regulation of OGG1 expression and activity in human cells and is involved mainly in the regulation of APE1 localization in mice. Aditionally, the response of NER deficient cells under oxidative stress may not be only associated to the NER deficiency per se, but it may include the new functions of NER enzymes in regulation of expression and cell localization of BER proteins / A maior parte do nosso conhecimento sobre a via de Reparo de Excis?o Nucleot?deos (NER) vem de estudos usando a luz ultravioleta (UV) como fonte de danos no DNA. Contudo, embora os danos no DNA causados pela luz UV sejam relacionados ? ocorr?ncia de mutag?nese, morte celular e tumorig?nese, eles n?o justificam fen?tipos como neurodegenera??o e tumorig?nese observados em pacientes com s?ndromes como Xeroderma Pigmentosum (XP) e S?ndrome de Cockayne (CS), as quais s?o associadas ? defici?ncia na via NER. Adicionalmente, evid?ncias mais recentes indicam o envolvimento da via NER no reparo de 8-oxodG, um substrato t?pico da via de Reparo por Excis?o de Bases (BER). Uma vez que a defici?ncia na via BER resulta em instabilidade gen?mica, doen?as neurodegenerativas e c?ncer, foi investigado neste trabalho o impacto da defici?ncia em XPC nas fun??es da via BER em c?lulas humanas. Foram realizadas an?lises da express?o e da localiza??o celular de APE1, OGG1 e PARP-1, principais enzimas da via BER, em fibroblastos humanos deficientes na via NER. Os resultados demonstraram que os n?veis end?genos de APE1, PARP-1 e OGG1 s?o reduzidos nos fibroblastos deficientes em XPC, os quais foram mais resistentes a diferentes tipos de agentes oxidantes e apresentaram n?veis elevados de 8-oxodG quando comparados aos demais fibroblastos deficientes na via NER. Adicionalmente, altera??es sutis na localiza??o nuclear e mitocondrial de APE1 foram observadas nos fibroblastos deficientes em XPC. Para confirmar o impacto da defici?ncia de XPC na regula??o da express?o e atividade de APE1 e OGG1, foi constru?da uma linhagem complementada com XPC. Embora a complementa??o tenha sido parcial, foi poss?vel observar que os fibroblastos parcialmente complementados com XPC apresentaram n?veis maiores de express?o de OGG1 quando comparados aos fibroblastos deficientes em XPC. Os extratos dos fibroblastos parcialmente complementados com XPC tamb?m apresentaram uma elevada atividade enzim?tica de OGG1. Contudo, n?o foram observadas mudan?as na express?o e atividade de APE1 nos fibroblastos parcialmente complementados com XPC. Adicionalmente, foi poss?vel verificar a presen?a da forma completa de APE1 (37 kDa) e de OGG1-? na mitoc?ndria dos fibroblastos deficientes em XPC e parcialmente complementados com XPC. Por outro lado, observou-se que a express?o de APE1 e PARP-1 n?o ? alterada no c?rebro e f?gado de camundongos knockouts para XPC. Contudo, a defici?ncia em XPC resultou em mudan?as na localiza??o celular de APE1 no hipocampo e hipot?lamo. Ainda, foi observada a ocorr?ncia de uma intera??o f?sica entre as prote?nas XPC e APE1 em c?lulas humanas. Em conclus?o, os dados sugerem que a prote?na XPC possui um papel na regula??o da express?o e da atividade de OGG1 em c?lulas humanas e est? envolvida na regula??o da localiza??o celular de APE1 principalmente em camundongos. Adicionalmente, as respostas celulares dos fibroblastos deficientes na via NER ao estresse oxidativo podem n?o estar associadas ? defici?ncia na via NER per se, mas podem incluir novas fun??es das enzimas da via NER na regula??o da express?o e localiza??o celular das prote?nas da via BER / 2020-01-01