Year: 2006
Type: article
Abstract: E. coli UmuD2 cleaves off its N-terminal 24 amino acids to form UmuD′2, which activates UmuC for its role in UV-mutagenesis. Cells with a non-cleavable UmuD exhibit essentially no UV-induced mutagenesis and are hypersensitive to killing by UV light. UmuD binds to the β processivity clamp (“β”) of DNA pol III. A possible β-binding motif has been predicted in the same region of UmuD shown to be important for its interaction with β. Alanine-scanning mutagenesis of this motif in UmuD (14TFPLF18) showed that the motif has a moderate effect on UV-induced mutagenesis but is required for the cold sensitive phenotype caused by elevated levels of wild-type UmuD and UmuC. Surprisingly, the wild-type and the β-motif variant bind to β with similar Kd values, but the single tryptophan in β is in different environments in the presence of the wild-type versus the variant UmuD proteins. Despite the fact that this UmuD variant is non-cleavable, cells harboring it display phenotypes more consistent with the cleaved form UmuD′, such as resistance to killing by UV light and loss of the cold sensitive phenotype. Cross-linking and chemical modification experiments indicate that the N-terminal arms of the UmuD variant are less likely to be bound to the globular domain than those of the wild-type, which may be the mechanism by which this UmuD variant acts as a UmuD′ mimic. Supported by NCI and NIEHS (from the MIT CEHS) to G.C.W.; a Damon Runyon Cancer Research Foundation fellowship to P.J.B.; a Cleo and Paul Schimmel Fellowship to S.M.S.; and the U.S. DoE to the Univ. of California, LLNL.
Source: The FASEB Journal
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1492537884