Histone H2AX is a critical factor for cellular protection against DNA alkylating agents

Abstract

Histone H2A variant H2AX is a dose-dependent suppressor of oncogenic chromosome translocations. H2AX participates in DNA double-strand break repair, but its role in other DNA repair pathways is not known. In this study, role of H2AX in cellular response to alkylation DNA damage was investigated. Cellular sensitivity to two monofunctional alkylating agents (methyl methane sulfonate and N-methyl-N 0 -nitro-N-nitrosoguanidine (MNNG)) was dependent on H2AX dosage, and H2AX null cells were more sensitive than heterozygous cells. In contrast to wild-type cells, H2AX-deficient cells displayed extensive apoptotic death due to a lack of cell-cycle arrest at G 2 /M phase. Lack of G 2 /M checkpoint in H2AX null cells correlated well with increased mitotic irregularities involving anaphase bridges and gross chromosomal instability. Observation of elevated poly(ADP) ribose polymerase 1 (PARP-1) cleavage suggests that MNNG-induced apoptosis occurs by PARP-1-dependent manner in H2AX-deficient cells. Consistent with this, increased activities of PARP and poly(ADP) ribose (PAR) polymer synthesis were detected in both H2AX heterozygous and null cells. Further, we demonstrate that the increased PAR synthesis and apoptotic death induced by MNNG in H2AX-deficient cells are due to impaired activation of mitogen-activated protein kinase pathway. Collectively, our novel study demonstrates that H2AX, similar to PARP-1, confers cellular protection against alkylation-induced DNA damage. Therefore, targeting either PARP-1 or histone H2AX may provide an effective way of maximizing the chemotherapeutic value of alkylating agents for cancer treatment.

Histone H2AX: The missing link in AIF-mediated caspase-independent programmed necrosis

“…Moreover, H2AX-deficient cells are more sensitive to apoptotic PCD than WT cells. 79 In caspase-independent necrotic PCD, both PARP-1-and H2AX-deficient…”

The apoptotic ring: A novel entity with phosphorylated histones H2AX and H2B, and activated DNA damage response kinases

“…22 On the other hand, H2AX-deficient fibroblasts are more sensitive to etoposide; 23 H2AX knockout mice are more sensitive to ionizing radiations; 24 and H2AX-null cells are hypersensitive to DNA alkylating agents, suggesting that H2AX confers cellular protection against alkylation-induced DNA damage. 25 Likewise, knockdown of H2AX in HCT116 cells enhances oxaliplatin-induced cell death (cell viability determined by MTT assay). 26 However, when we investigated H2AX's functional involvement in TRAILinduced apoptosis using H2AX siRNA (Fig.…”

Effect of curcumin on irradiated and estrogen-transformed human breast cell lines

“…The H2AX, member of the family H2A, is a subunit of the nucleosome. The phosphorylation of this protein at the serine 139 in the C-tail serine-glutamine-glutamate motif is one of the earliest responses of mammalian cells to ionizing radiation-induced DNA double-stand breaks (DSB) (35)(36)(37). H2AX forms discrete foci at the sites of DSBs, facilitates the remodeling complexes to the sites of DNA damage, and influences both the efficiency and fidelity of DSB repair.…”

“…Accumulation of phosphorylated histone H2AX, also called γ-H2AX, is a marker for DSB (35)(36)(37). The H2AX, member of the family H2A, is a subunit of the nucleosome.…”

“…The DNA damage response is a complex process involving multiple DNA repair, cell survival, and cell death pathways with damage specificity to different types of DNA damage (34)(35)(36)(37). The DNA damage includes double-strand breaks (DSB), single strand breaks, base damage, bulky adducts, intra/interstrand cross links, and breakdown of replication fork lesions where one of the key proteins in the base excision repair pathway is the Poly adenosine diphosphate ribose polymerase-1 (PARP-1) (6,19,(32)(33)(34).…”