Bunsyo Shiotani

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ATM and ATR are two master checkpoint kinases activated by double-stranded DNA breaks (DSBs). ATM is critical for the initial response and the subsequent ATR activation. Here we show that ATR activation is coupled with loss of ATM activation, an unexpected ATM-to-ATR switch during the biphasic DSB response. ATM is activated by DSBs with blunt ends or short(More)
The ataxia telangiectasia-mutated and Rad3-related (ATR) kinase is a master checkpoint regulator safeguarding the genome. Upon DNA damage, the ATR-ATRIP complex is recruited to sites of DNA damage by RPA-coated single-stranded DNA and activated by an elusive process. Here, we show that ATR is transformed into a hyperphosphorylated state after DNA damage,(More)
Chk1 is a kinase crucial for genomic integrity and an effector of ATR (ATM and Rad3-related) in DNA damage response. Here, we show that Chk1 regulates the DNA damage-induced ubiquitination of proliferating cell nuclear antigen (PCNA), which facilitates the continuous replication of damaged DNA. Surprisingly, this Chk1 function requires the DNA replication(More)
The maintenance of genomic integrity is crucial for the survival of all organisms. In humans, compromised genomic integrity contributes to genetic disorders, aging and cancers. The task of safeguarding the genome is accomplished by the concerted action of a number of cellular processes, including DNA replication, DNA repair, senescence and apoptosis. Many,(More)
Cells from Fanconi anemia (FA) patients are extremely sensitive to DNA interstrand crosslinking (ICL) agents, but the molecular basis of the hypersensitivity remains to be explored. FANCM (FA complementation group M), and its binding partner, FAAP24, anchor the multisubunit FA core complex to chromatin after DNA damage and may contribute to ICL-specific(More)
The ATM- and Rad3-related (ATR) kinase is a master regulator of the DNA damage response, yet how ATR is activated toward different substrates is still poorly understood. Here, we show that ATR phosphorylates Chk1 and RPA32 through distinct mechanisms at replication-associated DNA double-stranded breaks (DSBs). In contrast to the rapid phosphorylation of(More)
Inhibitors of poly(ADP-ribose) polymerase (PARP) are promising anticancer drugs, particularly for the treatment of tumors deficient in the DNA damage response (DDR). However, it is challenging to design effective therapeutic strategies for use of these compounds against cancers without DDR deficiencies. In this context, combination therapies in which PARP(More)
Homeobox 9 (HOXB9), a nontransforming transcription factor overexpressed in breast cancer, alters tumor cell fate and promotes tumor progression and metastasis. Here we show that HOXB9 confers resistance to ionizing radiation by promoting DNA damage response. In nonirradiated cells, HOXB9 induces spontaneous DNA damage, phosphorylated histone 2AX and p53(More)
The cabbage butterfly (Pieris rapae) produces pierisin-1, an apoptosis-inducing protein against mammalian cells. In order to clarify the biological role of pierisin-1 in P. rapae, its expression during developmental stages was examined. Low levels of pierisin-1 mRNA and protein were detected in first-instar larvae. During growth until the fifth-instar(More)
CBP-93872 was previously identified as a G2 checkpoint inhibitor using a cell-based high-throughput screening system. However, its molecular actions as well as cellular targets are largely unknown. Here, we uncovered the molecular mechanisms underlying abrogation of the G2 checkpoint by CBP-93872. CBP-93872 specifically abrogates the DNA double-stranded(More)