W. Rathmell
Last active: 11/27/2019

Ku86 defines the genetic defect and restores X-ray resistance and V(D)J recombination to complementation group 5 hamster cell mutants.

Errami A, Smider V, Rathmell WK, He DM, Hendrickson EA, Zdzienicka MZ, Chu G
Mol Cell Biol. 1996 16 (4): 1519-26

PMID: 8657125 · PMCID: PMC231136 · DOI:10.1128/mcb.16.4.1519

X-ray-sensitive hamster cells in complementation groups 4, 5, 6, and 7 are impaired for both double-strand break repair and V(D)J recombination. Here we show that in two mutant cell lines (XR-V15B and XR-V9B) from group 5, the genetic defects are in the gene encoding the 86-kDa subunit of the Ku autoantigen, a nuclear protein that binds to the double-stranded DNA ends. These mutants express Ku86 mRNA containing deletions of 138 and 252 bp, respectively, and the encoded proteins contain internal, in-frame deletions of 46 and 84 amino acids. Two X-ray-resistant revertants of XR-V15B expressed two Ku86 transcripts, one with and one without the deletion, suggesting that reversion occurred by activation of a silent wild-type allele. Transfection of full-length cDNA encoding hamster Ku86 into XR-V15B cells resulted in a complete rescue of DNA-end-binding (DEB) activity and Ku70 levels, suggesting that Ku86 stabilizes the Ku70 polypeptide. In addition, cells expressing wild-type levels of DEB activity were fully rescued for X-ray resistance and V(D)J recombination, whereas cells expressing lower levels of DEB activity were only partially rescued. Thus, Ku is an essential component of the pathway(s) utilized for the resolution of DNA double-strand breaks induced by either X rays or V(D)J recombination, and mutations in the Ku86 gene are responsible for the phenotype of group 5 cells.

MeSH Terms (19)

Amino Acid Sequence Animals Antigens, Nuclear Autoantigens Base Sequence Cell Survival Cricetinae Cricetulus DNA-Binding Proteins DNA Helicases DNA Nucleotidyltransferases Genetic Complementation Test Ku Autoantigen Molecular Sequence Data Mutation Nuclear Proteins Radiation Tolerance Sequence Alignment VDJ Recombinases

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