Role And Mechanism Of XPC Deficiency In Chromosome Aberration

Genomic DNA are continuously assaulted by all kinds of exogenous and endogenousdamages. Once, the damages are not rightly repaired or misrepaired, the accumulatedlesions may lead to mutations or even chromosome aberration. Chromosome aberrationinclude abnormalities in chromosome structures and chromosome numbers. Among thenumerous factors that lead to chromosome aberration, DNA double-strand breaks which isthe severest damages can directly lead to deletion and such damages which are not repairedor rightly repaired may lead to chromosome translocation and inversion. The abnormalmitotic spindle caused by centrosome amplification can always lead to aneuploidy.As a hallmark of tumor, chromosome aberration play an important role in theprogression of cancer.Therefore,to explore the mechanisms maintaining genomic stabilitymay help us find some new strategy to cope with cancer. We have previously found thatchromosome aberrations such as loss of heterogeneity are quite common in bladder cancertissues. Meantime, our data from immunohistochemical analysis indicated that theexpression of XPC is significantly low.Therefore, we hypothesized that XPC may be animportant cause of chromosome aberration or may interfere with the process ofchromosome aberration.As an recognising protein in Nucleotide excision repair,latest research indicate thatXPC may involved in cell cycle regulation;apoptosis; chromatin remodling and other repairpathway.Moreover,some recent data suggest that XPC may involved in DNA double-strandbreaks, but the related mechanisms are unknown. Also, as a vital role of XPC in cell cycleregulation that interfere with centrosome amplification. We speculate that XPC may involvein chromosome aberration via influencing the efficacity of DSB repair and centrosomeamplification.Baed on the above hypothesis, we established the XPC-deficient HEK293and T24cellstrains via lentiviral vector-mediated expression of small hairpin RNA against XPC.Usingdifferent damage agents (such as cispalin; Bleomycin; Etoposide) to investigate whether XPC deficiency could influence the efficacity of DSB repair and centrosome amplificationand explore the related mechanism.Our results are as follows:1． We verify that XPC deficiency could cause chromosome aberrations via themicronuclei or Giemsa karyotype analysis.2． XPC deficiency could cause high ratio of centrosome amplification viaImmunofluorescence analysis.3．We firstly found that XPC deficiency decreases the recruitment of some key factors(p-ATM Rad51) of DSB repair pathway to the damaged DNA via Immunofluorescenceanalysis.4．We show that XPC deficiency lowered the expression or shortened the active formof some key factors （ATM ATR p-ATM p-BRCA1BRCA2RAD51centrin2p-p53DNA-PKcs）among DSB repair pathway.5．We found that XPC deficiency extended the cell cycle arrest of S and G2/M phaseand WB analysis found that the expression of CDK1and activity of CDK2kinase are highlyelevated. Meantime, the DNA damage response protein p-ATM; p-p53are abnormallyactivated.ConclusionWe found that XPC deficiency interfere with the process of chromosome aberration.On one hand, XPC deficiency could affect the stability of chromosome structure viadisturbing the key repair proteins to decrease the efficacity of DSB repair; On the otherhand, XPC may affect centrosome amplification by disturbing the cell cycle or its relatedproteins to cause chromosome missegregation which can lead to aneuploidy.