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ABSTRACT: Heterogeneous nuclear ribonucleoprotein U-like 1 (hnRPUL1) -also known as adenovirus early region 1B-associated proteins 5 (E1B-AP5) - plays a role in RNA metabolism. Recently, hnRPUL1 has also been shown to be involved in DNA damage response, but the function of hnRPUL1 in response to DNA damage remains unclear. Here, we have demonstrated that hnRPUL1 is associated with PARP1 and recruited to DNA double-strand breaks (DSBs) sites in a PARP1-mediated poly (ADP-ribosyl) ation dependent manner. In turn, hnRPUL1 knockdown enhances the recruitment of PARP1 to DSBs sites. Specifically, we showed that hnRPUL1 is also implicated in the transcriptional regulation of PARP1 gene. Thus, we propose hnRPUL1 as a new component related to PARP1 in DNA damage response and repair.
PLoS ONE 01/2013; 8(4):e60208. · 4.09 Impact Factor
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ABSTRACT: BRCA1 is the first susceptibility gene to be linked to breast and ovarian cancers. Although mounting evidence has indicated that BRCA1 participates in DNA double-strand break (DSB) repair pathways, its precise mechanism is still unclear. Here, we analyzed the in situ response of BRCA1 at DSBs produced by laser microirradiation. The amino (N)- and carboxyl (C)-terminal fragments of BRCA1 accumulated independently at DSBs with distinct kinetics. The N-terminal BRCA1 fragment accumulated immediately after laser irradiation at DSBs and dissociated rapidly. In contrast, the C-terminal fragment of BRCA1 accumulated more slowly at DSBs but remained at the sites. Interestingly, rapid accumulation of the BRCA1 N terminus, but not the C terminus, at DSBs depended on Ku80, which functions in the nonhomologous end-joining (NHEJ) pathway, independently of BARD1, which binds to the N terminus of BRCA1. Two small regions in the N terminus of BRCA1 independently accumulated at DSBs and interacted with Ku80. Missense mutations found within the N terminus of BRCA1 in cancers significantly changed the kinetics of its accumulation at DSBs. A P142H mutant failed to associate with Ku80 and restore resistance to irradiation in BRCA1-deficient cells. These might provide a molecular basis of the involvement of BRCA1 in the NHEJ pathway of the DSB repair process.
Molecular and cellular biology 11/2008; 28(24):7380-93. · 6.06 Impact Factor
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ABSTRACT: Mismatch repair (MMR) proteins contribute to genome stability by excising DNA mismatches introduced by DNA polymerase. Although MMR proteins are also known to influence cellular responses to DNA damage, how MMR proteins respond to DNA damage within the cell remains unknown. Here, we show that MMR proteins are recruited immediately to the sites of various types of DNA damage in human cells. MMR proteins are recruited to single-strand breaks in a poly(ADP-ribose)-dependent manner as well as to double-strand breaks. Using mutant cells, RNA interference and expression of fluorescence-tagged proteins, we show that accumulation of MutSbeta at the DNA damage site is solely dependent on the PCNA-binding domain of MSH3, and that of MutSalpha depends on a region near the PCNA-binding domain of MSH6. MSH2 is recruited to the DNA damage site through interactions with either MSH3 or MSH6, and is required for recruitment of MLH1 to the damage site. We found, furthermore, that MutSbeta is also recruited to UV-irradiated sites in nucleotide-excision-repair- and PCNA-dependent manners. Thus, MMR and its proteins function not only in replication but also in DNA repair.
Journal of Cell Science 10/2008; 121(Pt 19):3146-54. · 6.11 Impact Factor
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ABSTRACT: DNA double-strand breaks (DSBs) represent the most toxic DNA damage arisen from endogenous and exogenous genotoxic stresses and are known to be repaired by either homologous recombination or nonhomologous end-joining processes. Although many proteins have been identified to participate in either of the processes, the whole processes still remain elusive. Polycomb group (PcG) proteins are epigenetic chromatin modifiers involved in gene silencing, cancer development and the maintenance of embryonic and adult stem cells. By screening proteins responding to DNA damage using laser micro-irradiation, we found that PHF1, a human homolog of Drosophila polycomb-like, Pcl, protein, was recruited to DSBs immediately after irradiation and dissociated within 10 min. The accumulation at DSBs is Ku70/Ku80-dependent, and knockdown of PHF1 leads to X-ray sensitivity and increases the frequency of homologous recombination in HeLa cell. We found that PHF1 interacts physically with Ku70/Ku80, suggesting that PHF1 promotes nonhomologous end-joining processes. Furthermore, we found that PHF1 interacts with a number of proteins involved in DNA damage responses, RAD50, SMC1, DHX9 and p53, further suggesting that PHF1, besides the function in PcG, is involved in genome maintenance processes.
Nucleic Acids Research 06/2008; 36(9):2939-47. · 8.03 Impact Factor
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ABSTRACT: DNA damage causes genome instability and cell death, but many of the cellular responses to DNA damage still remain elusive. We here report a human protein, PALF (PNK and APTX-like FHA protein), with an FHA (forkhead-associated) domain and novel zinc-finger-like CYR (cysteine-tyrosine-arginine) motifs that are involved in responses to DNA damage. We found that the CYR motif is widely distributed among DNA repair proteins of higher eukaryotes, and that PALF, as well as a Drosophila protein with tandem CYR motifs, has endo- and exonuclease activities against abasic site and other types of base damage. PALF accumulates rapidly at single-strand breaks in a poly(ADP-ribose) polymerase 1 (PARP1)-dependent manner in human cells. Indeed, PALF interacts directly with PARP1 and is required for its activation and for cellular resistance to methyl-methane sulfonate. PALF also interacts directly with KU86, LIGASEIV and phosphorylated XRCC4 proteins and possesses endo/exonuclease activity at protruding DNA ends. Various treatments that produce double-strand breaks induce formation of PALF foci, which fully coincide with gammaH2AX foci. Thus, PALF and the CYR motif may play important roles in DNA repair of higher eukaryotes.
The EMBO Journal 04/2007; 26(8):2094-103. · 9.20 Impact Factor
