Project description:The A-type lamins (lamin A/C), encoded by the Lmna gene, are important structural components of the nuclear lamina. Lmna mutations lead to degenerative disorders, including the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). In addition, altered lamin A/C expression is found in various cancers. Reports indicate that lamin A/C plays a role in DNA double strand break repair, but a role in DNA base excision repair (BER) has not been described. We provide evidence for reduced BER efficiency in lamin A/C-depleted cells. The mechanism involves impairment of the APE1 and POLβ enzyme activities in BER. Also, Lmna null mouse fibroblasts displayed reduced expression of several core BER enzymes (PARP1, LIG3, and POLβ). Moreover, the robustness of APE1 and POLβ activities and the rate of BER were enhanced by lamin A/C-augmented poly(ADP-ribose) polymer formation (PARylation). Finally, we report that HGPS fibroblasts are defective in BER. Collectively, our results provide novel insights into the functional interplay between the nuclear lamina and cellular defenses against oxidative DNA damage, with implications for human cancer and aging.
Project description:The A-type lamins (lamin A/C), encoded by the Lmna gene, are important structural components of the nuclear lamina. Lmna mutations lead to degenerative disorders, including the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). In addition, altered lamin A/C expression is found in various cancers. Reports indicate that lamin A/C plays a role in DNA double strand break repair, but a role in DNA base excision repair (BER) has not been described. We provide evidence for reduced BER efficiency in lamin A/C-depleted cells. The mechanism involves impairment of the APE1 and POLβ enzyme activities in BER. Also, Lmna null mouse fibroblasts displayed reduced expression of several core BER enzymes (PARP1, LIG3, and POLβ). Moreover, the robustness of APE1 and POLβ activities and the rate of BER were enhanced by lamin A/C-augmented poly(ADP-ribose) polymer formation (PARylation). Finally, we report that HGPS fibroblasts are defective in BER. Collectively, our results provide novel insights into the functional interplay between the nuclear lamina and cellular defenses against oxidative DNA damage, with implications for human cancer and aging.
Project description:We are investigating the transcriptional response of yeast to modulation of the expression of base excision repair players, these generate different dna lesions of abasic sites of strand breaks; We used microarrays to detail the global programme of gene expression underlying the DNA damage response in yeast Experiment Overall Design: Yeaststrains with different expression levels of players in base excision repair (in biological triplicate) were grown to mid log phase. The expression responses were compared to each other and we have deciphered a gene expression profile that is specific for DNA damage in yeast.
Project description:We are investigating the transcriptional response of yeast to modulation of the expression of base excision repair players, these generate different dna lesions of abasic sites of strand breaks We used microarrays to detail the global programme of gene expression underlying the DNA damage response in yeast Keywords: dose
Project description:DNA base damage arises frequently in all living cells and is an important contributor to mutations and genome instability. The main repair pathway for base damage is base excision repair (BER). How the formation and repair of base lesions are modulated by DNA-binding proteins is poorly understood. Here we used a high-throughput damage mapping method, N-methylpurine-sequencing (NMP-seq), to characterize alkylation damage distribution and BER at yeast transcription factor (TF) binding sites upon the treatment with alkylating agent methyl methanesulfonate (MMS). We found that formation of alkylation damage was mainly suppressed at the binding sites of yeat TFs Abf1 and Reb1, but individual hotspots with elevated damage formation were also observed. Furthermore, our data indicates that repair of alkyhlation damage by BER was significantly inhibited both within the TF core motif and its adajcent DNA. The modulation of damage formation and BER was caused by the TF binding, because lesion formation and repair can be restored by depletion of Abf1 or Reb1 from the nucleus. Finally, we show that repair of UV damage by nucleotide excision repair (NER) was also inhibited at the binding sites of Abf1 and Reb1. A comparision between alkylyation and UV damage repair reveals that NER was inhibited in a broader DNA region relative to BER. Thus, our analyses indicate that TF binding significantly modulates alkylation damage formation and inhibits repair by the BER pathway. The interplay between base damage formation and BER may play an important role in affecting mutation frequency in gene regulatory regions.
Project description:Nucleosomes are a significant barrier to the repair of UV damage because they impede damage recognition by nucleotide excision repair (NER). The RSC and SWI/SNF chromatin remodelers function in cells to promote DNA access by moving or evicting nucleosomes and both have been linked to NER in yeast. Here, we report genome-wide repair maps of UV-induced cyclobutane pyrimidine dimers (CPDs) in yeast cells lacking RSC or SWI/SNF activity. Our data indicate that SWI/SNF is not generally required for NER, but instead promotes repair of CPD lesions at specific yeast genes. In contrast, mutation or depletion of RSC subunits causes a general defect in NER across the yeast genome. Our data indicate that RSC is required for repair not only in nucleosomal DNA, but also neighboring linker DNA and nucleosome-free regions (NFRs). Intriguingly, while depletion of the RSC catalytic subunit also affects base excision repair (BER) of N-methylpurine (NMP) lesions, RSC activity is less important for BER in linker DNA and NFRs. Furthermore, our data indicate that RSC plays a direct role in transcription coupled-NER (TC-NER) of transcribed DNA. These findings help to define the specific genomic and chromatin contexts in which each chromatin remodeler functions in DNA repair, and indicate that RSC plays a unique function in facilitating repair by both NER subpathways.