A cooperative activation loop among SWI/SNF, γ-H2AX and H3 acetylation for DNA double-strand break repair

Abstract

Although recent studies highlight the importance of histone modifications and ATP-dependent chromatin remodelling in DNA double-strand break (DSB) repair, how these mechanisms cooperate has remained largely unexplored. Here, we show that the SWI/SNF chromatin remodelling complex, earlier known to facilitate the phosphorylation of histone H2AX at Ser-139 (S139ph) after DNA damage, binds to c-H2AX (the phosphorylated form of H2AX)-containing nucleosomes in S139ph-dependent manner. Unexpectedly, BRG1, the catalytic subunit of SWI/SNF, binds to c-H2AX nucleosomes by interacting with acetylated H3, not with S139ph itself, through its bromodomain. Blocking the BRG1 interaction with c-H2AX nucleosomes either by deletion or overexpression of the BRG1 bromodomain leads to defect of S139ph and DSB repair. H3 acetylation is required for the binding of BRG1 to c-H2AX nucleosomes. S139ph stimulates the H3 acetylation on c-H2AX nucleosomes, and the histone acetyltransferase Gcn5 is responsible for this novel crosstalk. The H3 acetylation on c-H2AX nucleosomes is induced by DNA damage. These results collectively suggest that SWI/SNF, c-H2AX and H3 acetylation cooperatively act in a feedback activation loop to facilitate DSB repair.

Histone acetylation by CBP and p300 at double-strand break sites facilitates SWI/SNF chromatin remodeling and the recruitment of non-homologous end joining factors

“…This indicated that histone acetylation by CBP or p300 at DSB sites facilitates the recruitment of the SWI/SNF complex. This result is consistent with a report that nucleosomes containing gH2AX, and histone H3 with mutations in the acetylation sites, lack the ability to interact with the SWI/SNF complex (Lee et al, 2010). In summary, the present results strongly indicate that the CBP and p300 proteins function as HATs for histone H3 and H4 at DSB sites and facilitate the recruitment of the SWI/SNF chromatin remodeling complex.…”

“…This was confirmed by our system. DNA damage-induced acetylation of N-terminal lysines 9, 14, 18, 23 and 56 within histone H3 in mammalian cells was observed by immunoblot analysis (Das et al, 2009;Tjeertes et al, 2009;Yuan et al, 2009;Lee et al, 2010;Miller et al, 2010). However, the results were controversial.…”

“…The accessibility of proteins to DNA in vivo is regulated by cooperation between histone modification and alterations in the nucleosomal position (Osley and Shen, 2006). In fact, it was recently suggested that histone acetylation is required for the recruitment of the SWI/ SNF complex to DSB sites (Lee et al, 2010). SWI/SNF is a chromatin remodeling complex that enhances DSB repair (Park et al, 2006).…”

“…Furthermore, the INO80, SWR1 and RSC complexes are required for the recruitment of KU70/80 to DSB sites (Shim et al, 2005;van Attikum et al, 2007). It is also suggested that the SWI/SNF complex is recruited to DSB sites, where it interacts with acetylated histone proteins and g-H2AX, a phosphorylated H2AX protein generated upon DSBs (Lee et al, 2010). Taken together, these studies suggest that histone acetylation facilitates chromatin remodeling and that the resulting 'relaxed' chromatin enables the recruitment of DNA repair proteins to DSB sites.…”

Regulation of Mec1 kinase activity by the SWI/SNF chromatin remodeling complex

“…Recruitment of ATP-dependent chromatin remodeling complexes to DSBs (Ray et al 2009;Lee et al 2010;Qi et al 2015) and the remodeling of the surrounding chromatin occur on a timescale similar to that of H2A phosphorylation. Moreover, it has been shown that the phosphorylation of Ies4 (a subunit of the INO80 chromatin remodeling complex) by Mec1/ Tel1 in response to DNA damage directs INO80 function toward checkpoint regulation (Morrison et al 2007).…”