The helicase domain and C-terminus of human RecQL4 facilitate replication elongation on DNA templates damaged by ionizing radiation

The vertebrate RECQL4 (RECQ4) gene is thought to be the ortholog of budding yeast SLD2. However, RecQL4 contains within its C-terminus a RecQ-like helicase domain, which is absent in Sld2. We established human pre-B lymphocyte Nalm-6 cells, in which the endogenous RECQL4 gene was homozygously targeted such that the entire C-terminus would not be expressed. The RECQL4(ΔC/ΔC) cells behaved like the parental cells during unperturbed DNA replication or after treatment with agents that induce stalling of DNA replication forks, such as hydroxyurea (HU). However, after exposure to ionizing radiation (IR), the RECQL4(ΔC/ΔC) cells exhibited hypersensitivity, inability to complete S phase and prematurely terminated or paused DNA replication forks. Deletion of BLM, a gene that also encodes a RecQ helicase, had the opposite phenotype; an almost wild-type response to IR, but hypersensitivity to HU. Targeting both R ECQL4 and BLM resulted in viable cells, which exhibited mostly additive phenotypes compared with those exhibited by the RECQL4(ΔC/ΔC) and the BLM(− /− ) cells. We propose that RecQL4 facilitates DNA replication in cells that have been exposed to I

DNA polymerases ν and θ are required for efficient immunoglobulin V gene diversification in chicken

Polν and Polθ have specialized functions in immunoglobulin gene rearrangements and only contribute to DNA repair when other homologous recombination–related DNA polymerases are absent

Fbh1 ヘリカーゼ ワ Blm ヘリカーゼ ト キョウリョクシテ フクセイ フォーク ホウカイ ニ ヨッテ ユウドウサレル クミカエ ニ タイオウスル

京都大学0048新制・課程博士博士(医学)甲第12915号医博第3075号新制||医||944(附属図書館)UT51-2007-H188京都大学大学院医学研究科生理系専攻(主査)教授 小松 賢志, 教授 丹羽 太貫, 教授 松本 智裕学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Comparison of the fertility of tumor suppressor gene-deficient C57BL/6 mouse strains reveals stable reproductive aging and novel pleiotropic gene

Abstract Tumor suppressor genes are involved in maintaining genome integrity during reproduction (e.g., meiosis). Thus, deleterious alleles in tumor suppressor-deficient mice would exhibit higher mortality during the perinatal period. A recent aging model proposes that perinatal mortality and age-related deleterious changes might define lifespan. This study aimed to quantitatively understand the relationship between reproduction and lifespan using three established tumor suppressor gene (p53, APC, and RECQL4)-deficient mouse strains with the same C57BL/6 background. Transgenic mice delivered slightly reduced numbers of 1st pups than wild-type mice [ratio: 0.81–0.93 (p = 0.1–0.61)] during a similar delivery period, which suggest that the tumor suppressor gene-deficient mice undergo relatively stable reproduction. However, the transgenic 1st pups died within a few days after birth, resulting in a further reduction in litter size at 3 weeks after delivery compared with that of wild-type mice [ratio: 0.35–0.68 (p = 0.034–0.24)] without sex differences, although the lifespan was variable. Unexpectedly, the significance of reproductive reduction in transgenic mice was decreased at the 2nd or later delivery. Because mice are easily affected by environmental factors, our data underscore the importance of defining reproductive ability through experiments on aging-related reproduction that can reveal a trade-off between fecundity and aging and identify RECQL4 as a novel pleiotropic gene

TopBP1 functions with 53BP1 in the G1 DNA damage checkpoint

The replication stress protein TopBP1 co-localizes with 53BP1 at sites of DNA damage and mediates its G1 cell cycle checkpoint function

Multiple Roles of Vertebrate REV Genes in DNA Repair and Recombination

In yeast, Rev1, Rev3, and Rev7 are involved in translesion synthesis over various kinds of DNA damage and spontaneous and UV-induced mutagenesis. Here, we disrupted Rev1, Rev3, and Rev7 in the chicken B-lymphocyte line DT40. REV1(−)(/)(−) REV3(−)(/)(−) REV7(−)(/)(−) cells showed spontaneous cell death, chromosomal instability/fragility, and hypersensitivity to various genotoxic treatments as observed in each of the single mutants. Surprisingly, the triple-knockout cells showed a suppressed level of sister chromatid exchanges (SCEs), which may reflect postreplication repair events mediated by homologous recombination, while each single mutant showed an elevated SCE level. Furthermore, REV1(−)(/)(−) cells as well as triple mutants showed a decreased level of immunoglobulin gene conversion, suggesting participation of Rev1 in a recombination-based pathway. The present study gives us a new insight into cooperative function of three Rev molecules and the Polζ (Rev3-Rev7)-independent role of Rev1 in vertebrate cells

The helicase domain and C-terminus of human RecQL4 facilitate replication elongation on DNA templates damaged by ionizing radiation

The vertebrate RECQL4 (RECQ4) gene is thought to be the ortholog of budding yeast SLD2. However, RecQL4 contains within its C-terminus a RecQ-like helicase domain, which is absent in Sld2. We established human pre-B lymphocyte Nalm-6 cells, in which the endogenous RECQL4 gene was homozygously targeted such that the entire C-terminus would not be expressed. The RECQL4(ΔC/ΔC) cells behaved like the parental cells during unperturbed DNA replication or after treatment with agents that induce stalling of DNA replication forks, such as hydroxyurea (HU). However, after exposure to ionizing radiation (IR), the RECQL4(ΔC/ΔC) cells exhibited hypersensitivity, inability to complete S phase and prematurely terminated or paused DNA replication forks. Deletion of BLM, a gene that also encodes a RecQ helicase, had the opposite phenotype; an almost wild-type response to IR, but hypersensitivity to HU. Targeting both RECQL4 and BLM resulted in viable cells, which exhibited mostly additive phenotypes compared with those exhibited by the RECQL4(ΔC/ΔC) and the BLM(-/-) cells. We propose that RecQL4 facilitates DNA replication in cells that have been exposed to IR.</p

Contribution of radiation education to anxiety reduction among Fukushima Daiichi Nuclear Power Plant workers: a cross sectional study using a text mining method

The purpose of this study is to investigate the frequency of education, knowledge of radiation and workplace anxiety of Fukushima Daiichi Nuclear Power Plant (FDNPP) workers and to analyze what type of words are used for anxiety with a text mining method. An original questionnaire survey was given to FDNPP workers, and a text mining method was used to extract information from free-entry felds.The questionnaires were collected from1135workers (responserate: 70.8%). It was found that when workers receive education on radiation, the increased knowledge helps to reduce their anxiety. Among the 1135workers, 92 of 127 completed the free-entry field with valid entries. Seventy-one wordswere extracted by the text mining method. The words used differed depending on the degree of anxiety. The text mining method revealed information about the presence or absence of radiation anxiety and the subjects’ working environment and background