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Previous issue date: 2016-09-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / No contexto da resposta ao estresse oxidativo, o reparo por excis?o de
bases (BER) ? considerado a principal via para o reparo de les?es oxidadas.
Entretanto, estudos indicam o papel do reparo por excis?o de nucleot?deos
(NER) na corre??o dessas les?es. Al?m disso, fatores do NER j? tiveram
fun??es descritas em outros processos biol?gicos, sendo importante que se
busque novas fun??es biol?gicas que possam ser associadas aos fen?tipos
das s?ndromes causadas por muta??es nos genes da via NER, dentre elas a
Xeroderma pigmentoso grupo de complementa??o A, associada a muta??es
em XPA, al?m da s?ndrome de Cockayne, ocasionada por muta??es no gene
CSB. Nesse contexto, c?lulas deficientes em XPA (XP12RO) ou CSB (CS1AN)
foram submetidas ao estresse oxidativo com per?xido de hidrog?nio (H2O2) e
apresentaram um perfil de sensibilidade ao agente, indicando que a aus?ncia
dessas prote?nas sensibilizou as linhagens a essa condi??o. A an?lise do
transcriptoma de c?lulas XP12RO indicou a diminui??o na express?o de genes
com papel na resposta ao dano no DNA e que promovem a sobreviv?ncia
celular em resposta ao estresse oxidativo. Nesse cen?rio, os resultados
indicaram que XPA pode atuar na regula??o da express?o de genes essenciais
? resposta ao dano no DNA e na sobreviv?ncia ao estresse oxidativo (EGR1,
GADD45A, GADD45B e XPC). Por outro lado, a an?lise do transcriptoma de
c?lulas CS1AN indicaram a diminui??o na express?o de genes-chave nos
processos biol?gicos como transcri??o, processamento de mRNA, prote?lise
via ubiquitina-proteassoma ou respira??o celular, indicando um poss?vel papel
central da prote?na CSB na regula??o desses processos, em resposta ao
estresse oxidativo. Al?m disso, dado o fen?tipo de neurodegenera??o
associada a s?ndrome de Cockayne, c?lulas progenitoras neurais (NPCs) e
neur?nios derivados de c?lulas-tronco pluripotentes induzidas (iPSCs)
deficientes em CSB foram utilizados como modelos de estudo de altera??es
neuronais in vitro, de modo que os resultados indicaram que assim como
observado nos fibroblastos, c?lulas NPCs deficientes em CSB tamb?m
apresentaram sensibilidade a agentes oxidantes. Ainda, os resultados
mostraram que assim como observado no transcriptoma de fibroblastos
CS1AN, dada a diminui??o na express?o de genes com papel na respira??o
celular, as an?lises do consumo de oxig?nio em neur?nios deficientes em CSB
indicaram uma poss?vel disfun??o mitocondrial, caracterizada pelo decr?scimo
na taxa de consumo de oxig?nio basal e pela diminui??o das capacidades
respirat?rias m?xima ou de reserva dessas c?lulas, sugerindo o papel de CSB
no metabolismo mitocondrial em ambos os modelos celulares utilizados neste
estudo. / In oxidative stress response, the base excision repair (BER) is
considered the major pathway for repair of oxidative lesions. However, an
increasing number of studies have indicated the role of nucleotide excision
(NER) in the repair of these lesions. In addition, some NER factors had
functions beyond the role in repair already described and it is important to
search for new molecular functions that can be associated to the classical
phenotypes of the syndromes caused by mutations in NER genes: Xeroderma
pigmentosum complementation group A, caused by mutations in XPA and
Cockayne syndrome, caused by mutations in CSB. In this context, XPA
(XP12RO) or CSB (CS1AN) deficient cells were submitted to oxidative stress
induced by Hydrogen peroxide (H2O2) and the results indicated that both cell
lines showed sensitivity to this agent. Furthermore, the transcriptome of
XP12RO cells revealed the downregulation of genes that play a role in DNA
damage response and promote cell survival in response to oxidative stress. In
this scenario, the results indicated that XPA regulates the expression of genes
that play a key role in DNA damage response and promote survival in response
to stress (EGR1, GADD45A, GADD45B and XPC). On the other hand, the
transcriptome analysis of CS1AN cells showed the downregulation of genes
that play a key role in biological processes such as transcription, mRNA
processing, protein degradation by the ubiquitin?proteasome pathway
proteolysis or cellular respiration, indicating a possible role for CSB protein in
the regulation of these processes, in response to oxidative stress. In adittion,
given the neurodegeneration phenotype associated to Cockayne syndrome,
neural progenitor cells (NPCs) and neurons derived from CSB deficient induced
pluripotent stem cells (iPSCs) were used as cellular models to analyse neuronal
changes in vitro. The results showed that, as observed in fibroblasts CS1AN,
NPCs also presented sensitivity to oxidizing agents. Furthermore, as indicated
in the transcriptome data from CS1AN fibroblasts, given the downregulation of
genes that play a pivotal role in cellular respiration, the analysis of oxygen
consumption rates in CSB deficient neurons also indicated a mitochondrial
dysfunction characterized by the decrease in oxygen consumption basal rate
and a lower maximum respiratory and reserve capacities, suggesting that the
lack of functional CSB leads to a mitochondrial dysfunction in both cellular
models used in this study. / 2017-12-09
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/22713 |
| Date | 29 September 2016 |
| Creators | Leal, Ang?lica Maria de Sousa |
| Contributors | 00297997750, http://lattes.cnpq.br/1083882171718362, Vessoni, Alexandre Teixeira, 36505971874, http://lattes.cnpq.br/8720495541846560, Machado, Carlos Renato, 71055886672, http://lattes.cnpq.br/6306925202374274, Costa, Marcos Romualdo, 05278916737, http://lattes.cnpq.br/6118493598074445, Dalmolin, Rodrigo Juliani Siqueira, 94020035091, http://lattes.cnpq.br/4065178015615979, Agnez, Lucymara Fassarella |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM BIOQU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/embargoedAccess |
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