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Chromatin remodelling is critical for repairing DNA damage and maintaining genomic integrity. Previous studies have reported that histone acetyltransferase p300 and ATP-dependent chromatin remodeler chromodomain helicase DNA-binding protein 4 (CHD4) functions, respectively, in DNA double-strand breaks (DSBs) repair. But the physiological significance of their interaction remains elusive. Here, we showed that p300 and CHD4 were both recruited to the sites of DSBs. Their ablation led to impaired DSBs repair and sensitised cells to laser and the anti-cancer drug, etoposide. Using DR-GFP and EJ5-GFP reporter systems, we found that knockdown of p300 or CHD4 impaired the homologous recombination (HR) repair but no the non-homologous end joining (NHEJ) repair. Furthermore, p300 or CHD4 knockdown respectively suppressed the recruitment of replication protein A (RPA), a key protein for HR, to the DSB sites. In addition, immunofluorescence results showed that knockdown of p300 reduced the recruitment of CHD4 at DSB sites. In turn, CHD4 knockdown also decreased p300 assembly. Moreover, immunoprecipitation and purified protein pull down assay revealed that p300 physically interacted with CHD4 at DNA damage sites, and this interaction was dependent on the chromodomain and ATPase/helicase domain of CHD4 and the CH2, Bd and HAT domains of p300. These results indicate that p300 and CHD4 could function cooperatively at DSB sites and provide a new insight into the detailed crosstalk among the chromatin remodelling proteins. [ABSTRACT FROM AUTHOR]

DNA double-strand breaks (DSBs) are a type of lethal DNA damage. The repair of DSBs requires tight coordination between the factors modulating chromatin structure and the DNA repair machinery. BRG1, the ATPase subunitof the chromatin remodelling complex Switch/Sucrose non-fermentable (SWI/SNF), is often linked to tumorigenesis and genome instability, and its role in DSB repair remains largely unclear. In the present study, we show that BRG1 is recruited to DSB sites and enhances DSB repair. Using DR-GFP and EJ5-GFP reporter systems, we demonstrate that BRG1 facilitates homologous recombination repair rather than nonhomologous end-joining (NHEJ) repair. Moreover, the BRG1-RAD52 complex mediates the replacement of RPA with RAD51 on single-stranded DNA (ssDNA) to initiate DNA strand invasion. Loss of BRG1 results in a failure of RAD51 loading onto ssDNA, abnormal homologous recombination repair and enhanced DSB-induced lethality. Our present study provides a mechanistic insight into how BRG1, which is known to be involved in chromatin remodelling, plays a substantial role in the homologous recombination repair pathway in mammalian cells. [ABSTRACT FROM AUTHOR]