Modulation of Werner syndrome protein function by a single mutation in the conserved RecQ domain |
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Authors: | Lee Jae Wan Kusumoto Rika Doherty Kevin M Lin Guang-Xin Zeng Wangyong Cheng Wen-Hsing von Kobbe Cayetano Brosh Robert M Hu Jin-Shan Bohr Vilhelm A |
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Affiliation: | Laboratory of Molecular Gerontology, NIA, National Institutes of Health, Baltimore, Maryland 21224-6825, USA. |
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Abstract: | Naturally occurring mutations in the human RECQ3 gene result in truncated Werner protein (WRN) and manifest as a rare premature aging disorder, Werner syndrome. Cellular and biochemical studies suggest a multifaceted role of WRN in DNA replication, DNA repair, recombination, and telomere maintenance. The RecQ C-terminal (RQC) domain of WRN was determined previously to be the major site of interaction for DNA and proteins. By using site-directed mutagenesis in the WRN RQC domain, we determined which amino acids might be playing a critical role in WRN function. A site-directed mutation at Lys-1016 significantly decreased WRN binding to fork or bubble DNA substrates. Moreover, the Lys-1016 mutation markedly reduced WRN helicase activity on fork, D-loop, and Holliday junction substrates in addition to reducing significantly the ability of WRN to stimulate FEN-1 incision activities. Thus, DNA binding mediated by the RQC domain is crucial for WRN helicase and its coordinated functions. Our nuclear magnetic resonance data on the three-dimensional structure of the wild-type RQC and Lys-1016 mutant proteins display a remarkable similarity in their structures. |
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