UV Damage-Induced Phosphorylation of HBO1 Triggers CRL4^DDB2-Mediated Degradation To Regulate Cell Proliferation

Abstract

e Histone acetyltransferase binding to ORC-1 (HBO1) is a critically important histone acetyltransferase for forming the prereplicative complex (pre-RC) at the replication origin. Pre-RC formation is completed by loading of the MCM2-7 heterohexameric complex, which functions as a helicase in DNA replication. HBO1 recruited to the replication origin by CDT1 acetylates histone H4 to relax the chromatin conformation and facilitates loading of the MCM complex onto replication origins. However, the acetylation status and mechanism of regulation of histone H3 at replication origins remain elusive. HBO1 positively regulates cell proliferation under normal cell growth conditions. Whether HBO1 regulates proliferation in response to DNA damage is poorly understood. In this study, we demonstrated that HBO1 was degraded after DNA damage to suppress cell proliferation. Ser50 and Ser53 of HBO1 were phosphorylated in an ATM/ATR DNA damage sensor-dependent manner after UV treatment. ATM/ATRdependently phosphorylated HBO1 preferentially interacted with DDB2 and was ubiquitylated by CRL4 DDB2 . Replacement of endogenous HBO1 in Ser50/53Ala mutants maintained acetylation of histone H3K14 and impaired cell cycle regulation in response to UV irradiation. Our findings demonstrate that HBO1 is one of the targets in the DNA damage checkpoint. These results show that ubiquitin-dependent control of the HBO1 protein contributes to cell survival during UV irradiation.T ight regulation of genome maintenance processes, including DNA repair, checkpoints, apoptosis, and cell cycle control, prevents DNA instability after DNA damage. Mammalian cells coordinately operate these systems for organism survival, in part through ataxia telangiectasia mutated (ATM) and ATM-and RAD3-related protein (ATR), two critical kinases that function as regulators of major checkpoint pathways. ATM is primarily activated by DNA double-strand breaks (DSBs) (1), and ATR is activated in response to inhibition of DNA replication (2). Activated ATM and ATR phosphorylate histone H2AX to recruit DNA repair proteins (3) and also checkpoint kinase 1 (Chk1) to suppress cell cycle progression (4, 5). Chk1 indirectly inhibits dephosphorylation of Tyr15 of cyclin-dependent kinase 2 (CDK2) (6) and CDC2 via Cdc25A degradation (7). ATM and ATR also phosphorylate the p53 tumor suppressor to increase its protein stability (8). p53 is a critical cellular factor that induces apoptosis genes (9) and the p21 CDK inhibitor gene (10, 11). Thus, substrates of ATM and ATR are involved in arresting the cell cycle, repairing DNA, and eliminating damaged cells by apoptosis.Histone acetyltransferase binding to ORC-1 (HBO1) was originally identified as an ORC1 binding protein (12) and acts as a cofactor in the prereplicative complex (pre-RC) (13). This histone acetyltransferase (HAT) associates with distinct complexes to acetylate histones H3 and H4 (14, 15). HBO1 is also involved in cell proliferation control through regulating the expression of multiple genes in the p53 pathway (16). A previous ...

Phosphorylated HBO1 at UV irradiated sites is essential for nucleotide excision repair

“…Although ubiquitylation of HBO1 by DDB2 leading to degradation appears from 2 h after ultraviolet irradiation15, HBO1 pS50/53 signals were detected on the chromatin at least 2 h after ultraviolet irradiation (Fig. 1b).…”

“…We previously reported that Ser50 and Ser53 of HBO1 were phosphorylated in response to various DNA damage treatments15. Based on these observations, we examined whether HBO1 is involved in survival against ionizing radiation (IR), which induces oxidative damage, single-strand breaks (SSBs) and some DSBs, or mitomycin C (MMC) treatment, which induces both inter- and intrastrand crosslinks.…”

Xeroderma pigmentosum group C protein interacts with histones: regulation by acetylated states of histone H3

“…) and KAT7/HBO1/MYST2 (Matsunuma et al . ), the histone deacetylases HDAC1/2 (Zhao et al . ; Zhu et al .…”

Histone Lysine and Genomic Targets of Histone Acetyltransferases in Mammals

“…[27][28][29] It was suggested that HBO1 can acetylate either H4 or H3K14 depending on the composition of the HBO1 protein complex partners. [21,22,[30][31][32] TIP60 can acetylate H2A-K5, H2A-K15, H3K14, H4K5, H4K8, H4K12, and H4K16 in cell-free assays, [33,34] but appears to be restricted to H2A-K5 in cells. [21,22,[30][31][32] TIP60 can acetylate H2A-K5, H2A-K15, H3K14, H4K5, H4K8, H4K12, and H4K16 in cell-free assays, [33,34] but appears to be restricted to H2A-K5 in cells.…”

“…In cells, shRNA KD shRNA depletion of HBO1 profound reduction in H3K14ac and H3K9ac, acetylation of H4K5 and 8 reduced to lesser degree [22] HBO1 H3K14 Genetic deletion, mouse cells Cells from Hbo1 null embryos, >90% reduction of H3K14ac, no reduction in acetylation of H4K5, 8, and 12, and upregulation of H4K16ac and H3K9ac [21] HBO1 H3K14 In cells, shRNA Depletion of HBO1 ablated H3K14ac in MLE cells [32] HBO1 H3K14 In cells, siRNA Depletion of HBO1 caused reduction in H3K14ac [30] HBO1 H3K14 Constitutive HBO1 HBO1 Ser50/53Ala mutant cells, deregulated H3K14ac [31] HBO1 H3K14 H4…”