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21. Inhibition in a microgravity environment of the recovery of Escherichia coli cells damaged by heavy ion beams during the NASDA ISS phase I program of NASA Shuttle/Mir mission no. 6.

Author

Harada, K, primary, Sugahara, T, additional, Ohnishi, T, additional, Ozaki, Y, additional, Obiya, Y, additional, Miki, S, additional, Miki, T, additional, Imamura, M, additional, Kobayashi, Y, additional, Watanabe, H, additional, Akashi, M, additional, Furusawa, Y, additional, Mizuma, N, additional, Yamanaka, H, additional, Ohashi, E, additional, Yamaoka, C, additional, Yajima, M, additional, Fukui, M, additional, Nakano, T, additional, Takahashi, S, additional, Amano, T, additional, Sekikawa, K, additional, Yanagawa, K, additional, and Nagaoka, S, additional

Published
1998
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27. Error-prone bypass of certain DNA lesions by the human DNA polymerase kappa.

Author

Ohashi, E, Ogi, T, Kusumoto, R, Iwai, S, Masutani, C, Hanaoka, F, and Ohmori, H

Abstract

The Escherichia coli protein DinB is a newly identified error-prone DNA polymerase. Recently, a human homolog of DinB was identified and named DINB1. We report that the DINB1 gene encodes a DNA polymerase (designated polkappa), which incorporates mismatched bases on a nondamaged template with a high frequency. Moreover, polkappa bypasses an abasic site and N-2-acetylaminofluorene (AAF)-adduct in an error-prone manner but does not bypass a cis-syn or (6-4) thymine-thymine dimer or a cisplatin-adduct. Therefore, our results implicate an important role for polkappa in the mutagenic bypass of certain types of DNA lesions.

Published
2000

49. Oxidative generation of isobenzofurans from phthalans: application to the formal synthesis of (±)-morphine.

Author

Kage M, Yamakoshi H, Tabata M, Ohashi E, Noguchi K, Watanabe T, Uchida M, Takada M, Ikeuchi K, and Nakamura S

Abstract

Treatment of phthalan derivatives with p -chloranil in dodecane in the presence of molecular sieves at 160-200 °C allowed the generation of unstabilized isobenzofurans, which underwent intramolecular Diels-Alder reaction to give endo cycloadducts exclusively. The cycloaddition turned out to be reversible, providing an equilibrium mixture of endo adducts when heating a substrate with a stereocenter on the tether. We also demonstrated the regioselective allylation of an oxygen-bridged cycloadduct upon exposure to EtAlCl 2 in the presence of allyltrimethylsilane, and the conversion to Rice's intermediate completed a formal synthesis of (±)-morphine., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Published
2024
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50. Resection of DNA double-strand breaks activates Mre11-Rad50-Nbs1- and Rad9-Hus1-Rad1-dependent mechanisms that redundantly promote ATR checkpoint activation and end processing in Xenopus egg extracts.

Author

Tatsukawa K, Sakamoto R, Kawasoe Y, Kubota Y, Tsurimoto T, Takahashi TS, and Ohashi E

Subjects
Animals, Cell Cycle Proteins genetics, Cell Cycle Proteins metabolism, DNA genetics, DNA metabolism, MRE11 Homologue Protein genetics, MRE11 Homologue Protein metabolism, Tumor Suppressor Proteins genetics, Tumor Suppressor Proteins metabolism, Xenopus laevis genetics, Chromosomal Proteins, Non-Histone genetics, Chromosomal Proteins, Non-Histone metabolism, Enzyme Activation genetics, Phosphorylation genetics, Ataxia Telangiectasia Mutated Proteins genetics, Ataxia Telangiectasia Mutated Proteins metabolism, DNA Breaks, Double-Stranded, DNA Repair Enzymes genetics, DNA Repair Enzymes metabolism, Xenopus Proteins genetics, Xenopus Proteins metabolism
Abstract

Sensing and processing of DNA double-strand breaks (DSBs) are vital to genome stability. DSBs are primarily detected by the ATM checkpoint pathway, where the Mre11-Rad50-Nbs1 (MRN) complex serves as the DSB sensor. Subsequent DSB end resection activates the ATR checkpoint pathway, where replication protein A, MRN, and the Rad9-Hus1-Rad1 (9-1-1) clamp serve as the DNA structure sensors. ATR activation depends also on Topbp1, which is loaded onto DNA through multiple mechanisms. While different DNA structures elicit specific ATR-activation subpathways, the regulation and mechanisms of the ATR-activation subpathways are not fully understood. Using DNA substrates that mimic extensively resected DSBs, we show here that MRN and 9-1-1 redundantly stimulate Dna2-dependent long-range end resection and ATR activation in Xenopus egg extracts. MRN serves as the loading platform for ATM, which, in turn, stimulates Dna2- and Topbp1-loading. Nevertheless, MRN promotes Dna2-mediated end processing largely independently of ATM. 9-1-1 is dispensable for bulk Dna2 loading, and Topbp1 loading is interdependent with 9-1-1. ATR facilitates Mre11 phosphorylation and ATM dissociation. These data uncover that long-range end resection activates two redundant pathways that facilitate ATR checkpoint signaling and DNA processing in a vertebrate system., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Published
2024
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