Human RECQ1 is a DNA damage responsive protein required for genotoxic stress resistance and suppression of sister chromatid exchanges.
BACKGROUND
DNA helicases are ubiquitous enzymes that unwind DNA in an ATP-dependent and directionally specific manner. Unwinding of double-stranded DNA is essential for the processes of DNA repair, recombination, transcription, and DNA replication. Five human DNA helicases sharing sequence similarity with the E. coli RecQ helicase have been identified. Three of the human RecQ helicases are implicated in hereditary diseases (Bloom syndrome, Werner syndrome, and Rothmund-Thomson syndrome) which display clinical symptoms of premature aging and cancer. RECQ1 helicase is the most highly expressed of the human RecQ helicases; however, a genetic disease has yet not been linked to mutations in the RECQ1 gene, and the biological functions of human RECQ1 in cellular DNA metabolism are not known.


RESULTS
In this study, we report that RECQ1 becomes phosphorylated upon DNA damage and forms irradiation-induced nuclear foci that associate with chromatin in human cells. Depletion of RECQ1 renders human cells sensitive to DNA damage induced by ionizing radiation or the topoisomerase inhibitor camptothecin, and results in spontaneous gamma-H2AX foci and elevated sister chromatid exchanges, indicating aberrant repair of DNA breaks. Consistent with a role in homologous recombinational repair, endogenous RECQ1 is associated with the strand exchange protein Rad51 and the two proteins directly interact with high affinity.


CONCLUSIONS
Collectively, these results provide the first evidence for a role of human RECQ1 in the response to DNA damage and chromosomal stability maintenance and point to the vital importance of RECQ1 in genome homeostasis.
Sharma
Sudha
S
Laboratory of Molecular Gerontology, Department of Health and Human Services, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.
Brosh
Robert M
RM
D001483:Base Sequence; D004249:DNA Damage; D006367:HeLa Cells; D006801:Humans; D009153:Mutagens / Q000633:toxicity*; D018384:Oxidative Stress; D034741:RNA, Small Interfering; D053484:RecQ Helicases / Q000235:genetics / Q000378:metabolism*; D012854:Sister Chromatid Exchange
D009153:Mutagens; D034741:RNA, Small Interfering; D053484:RecQ Helicases