Role for hACF1 in the G2/M damage checkpoint

Abstract

Active chromatin remodelling is integral to the DNA damage response in eukaryotes, as damage sensors, signalling molecules and repair enzymes gain access to lesions. A variety of nucleosome remodelling complexes is known to promote different stages of DNA repair. The nucleosome sliding factors CHRAC/ACF of Drosophila are involved in chromatin organization during development. Involvement of corresponding hACF1-containing mammalian nucleosome sliding factors in replication, transcription and very recently also non-homologous end-joining of DNA breaks have been suggested. We now found that hACF1-containing factors are more generally involved in the DNA damage response. hACF1 depletion increases apoptosis, sensitivity to radiation and compromises the G2/M arrest that is activated in response to UV- and X-rays. In the absence of hACF1, γH2AX and CHK2ph signals are diminished. hACF1 and its ATPase partner SNF2H rapidly accumulate at sites of laser-induced DNA damage. hACF1 is also required for a tight checkpoint that is induced upon replication fork collapse. ACF1-depleted cells that are challenged with aphidicolin enter mitosis despite persistence of lesions and accumulate breaks in metaphase chromosomes. hACF1-containing remodellers emerge as global facilitators of the cellular response to a variety of different types of DNA damage.

Poly(ADP-ribosyl)ation links the chromatin remodeler SMARCA5/SNF2H to RNF168-dependent DNA damage signaling

“…Recent work reported that SMARCA5 is recruited to DNA damage sites (Erdel et al, 2010;Lan et al, 2010;Nakamura et al, 2011;Sánchez-Molina et al, 2011). Chromatin immunoprecipitation (ChIP) coupled to quantitative PCR (qPCR) confirmed these results by showing SMARCA5 and cH2AX accumulation at two different sites flanking AsiSI-induced DSBs on chromosome 1 and 22 (supplementary material Fig.…”

“…1F; supplementary material Fig. S3C,D) (Erdel et al, 2010;Lan et al, 2010;Nakada et al, 2010;Sánchez-Molina et al, 2011). Nakamura and co-workers implicated a role for the RNF20 E3 ubiquitin ligase in SMARCA5 recruitment to DNA breaks (Nakamura et al, 2011), whereas, another report suggested a role for ACF1 in SMARCA5 recruitment to DSBs, although formally it was not shown that ACF1 loss abrogates SMARCA5 assembly at DSBs (Lan et al, 2010).…”

“…However, whether more downstream factors, such as RNF168 or BRCA1, also require chromatin-modifying activities is not known. Recently it was found that SMARCA5/SNF2H, the ATPase of several distinct ISWI chromatin remodeling complexes, is also involved in the DSB response (Lan et al, 2010;Nakamura et al, 2011;Sánchez -Molina et al, 2011). However, mechanistic insight into how SMARCA5 affects the signaling and repair of DSBs is currently limited.…”

Chromatin maintenance by a molecular motor protein

“…A structural role for KIF4 explains the previously reported activation of DNA damage signaling pathways in KIF4-null ES cells 14 likely brought about by replicationassociated defects in chromatin assembly. 32 In line with KIF4 mediated chromatin-associated S-phase defects, the observed chromatin phenotypes upon KIF4 loss are reminiscent of those seen in mutants of replication factors such as ORC2 or defective resolution of Holliday junctions in Bloom's syndrome cells. 33,34 The molecular interactions of chromokinesin KIF4 and the chromosome condensation and DNA replication machinery occur probably in the context of larger complexes since human KIF4A and condensin can be biochemically purified with condensin, the DNA methyltransferase DNMT3B, the chromatin remodelers SIN3A and hSNF2H and the histone deacetylase HDAC1.…”

Chromatin Remodeling in Nucleotide Excision Repair in Mammalian Cells

“…Moreover, SNF2H interacts with CSB [97], and the ACF1 subunit is recruited to UVC-induced DNA damage [98]. Knockdown of the mammalian ISWI ATPase SNF2H/SMARCA5 or its auxiliary factor ACF1/BAZ1A also leads to mild UVC sensitivity [99]. However, further experimental evidence is required to understand how ISWI chromatin remodeling functions in the UVC-DNA damage response.…”