Radiation-induced bystander effects have been observed in vitro and in cell and tissue culture models, however, there are few reported studies showing these effects in vivo. To our knowledge, this is the first reported study on bystander effects induced by microbeam irradiation in an intact living mammal. The mouse ear was used to investigate radiation-induced bystander effects in keratinocytes...

Replication-independent histone variants can replace the canonical replication-dependent histones. Vertebrates have multiple H2A variant histones, including H2AZ and H2AX that are present in most eukaryotes. H2AZ regulates transcriptional activation as well as the maintenance of gene silencing, while H2AX is important in DNA damage repair. The fruit fly Drosophila melanogaster has only one hist...

The mammalian E3 ubiquitin ligases RNF8 and RNF168 facilitate recruitment of the DNA damage response protein 53BP1 to sites of DNA double-strand breaks (DSBs). The mechanism involves recruitment of RNF8, followed by recruitment of RNF168, which ubiquitinates histones H2A/H2AX on K15. 53BP1 then binds to nucleosomes at sites of DNA DSBs by recognizing, in addition to methyl marks, histone H2A/H2...

Pancreatic cancer is an aggressive malignancy with a characteristic metastatic course of disease and resistance to conventional radiotherapy. As a result, the continual development of novel therapeutic agents is required to improve the current situation. In the present study, the effect of the hedgehog pathway inhibitor, cyclopamine, on cellular radiosensitivity was determined in K‑RASwt Colo‑3...

Gastrointestinal stromal tumors (GIST) are caused by activating mutations in the KIT or PDGFRA receptor tyrosine kinase genes. Although >85% of GIST patients treated with the small-molecule inhibitor imatinib mesylate (Gleevec) achieve disease stabilization, complete remissions are rare and a substantial proportion of patients develop resistance to imatinib over time. Upregulation of soluble, n...

The Bloom syndrome helicase (BLM) is critical for genomic stability. A defect in BLM activity results in the cancer-predisposing Bloom syndrome (BS). Here, we report that BLM-deficient cell lines and primary fibroblasts display an endogenously activated DNA double-strand break checkpoint response with prominent levels of phosphorylated histone H2AX (gamma-H2AX), Chk2 (p(T68)Chk2), and ATM (p(S1...

53BP1 is a well-known mediator of the cellular response to DNA damage. Two alternative mechanisms have been proposed to explain 53BP1's interaction with DNA double-strand breaks (DSBs), one by binding to methylated histones and the other via an RNF8 E3 ligase-dependent ubiquitylation pathway. The formation of RNF8 and 53BP1 irradiation-induced foci are both dependent on histone H2AX. To evaluat...

A comparative investigation of the induction of double-strand DNA breaks (DSBs) in the Chinese hamster V79 cells by γ-radiation at dose rates of 1, 10 and 400 mGy/min (doses ranged from 0.36 to 4.32 Gy) was performed. The acute radiation exposure at a dose rate of 400 mGy/min resulted in the linear dose-dependent increase of the γ-H2AX foci formation. The dose-response curve for the acute expos...

Histone variant H2AX phosphorylation in response to DNA damage is the major signal for recruitment of DNA-damage-response proteins to regions of damaged chromatin. Loss of H2AX causes radiosensitivity, genome instability, and DNA double-strand-break repair defects, yet the mechanisms underlying these phenotypes remain obscure. Here, we demonstrate that mammalian MDC1/NFBD1 directly binds to pho...

In mammalian spermatogenesis, the X and Y chromosomes are transcriptionally silenced during the pachytene stage of meiotic prophase (meiotic sex chromosome inactivation, MSCI), forming a condensed chromatin domain termed the sex or XY body. The nucleosomal core histone H2AX is phosphorylated within the XY chromatin domain just prior to MSCI, and it has been hypothesized that this triggers the c...