Abstract
Rad51/RadA paralogs found in eukaryotes and euryarchaea play important roles during recombination and repair, and mutations in one of the human Rad51 paralogs, Rad51C, are associated with breast and ovarian cancers. The hyperthermophilic crenarchaeon Sulfolobus tokodaii encodes four putative RadA paralogs and studies on these proteins may assist in understanding the functions of human Rad51 paralogs. Here, we report the biochemical characterization of stRadC2, a S. tokodaii RadA paralog. Pull-down assays revealed that the protein was able to interact with the recombinase, RadA, and the Holliday junction endonuclease, Hjc. stRadC2 inhibited the strand exchange activity of RadA and facilitated Hjc-mediated Holliday junction DNA cleavage in vitro. RT-PCR analysis revealed that stRadC2 transcription was immediately reduced after UV irradiation, but was restored to normal levels at the late stages of DNA repair. Our results suggest that stRadC2 may act as an anti-recombination factor in DNA recombinational repair in S. tokodaii.
Highlights
Rad51/RadA paralogs found in eukaryotes and euryarchaea play important roles during recombination and repair, and mutations in one of the human Rad51 paralogs, Rad51C, are associated with breast and ovarian cancers
Our results suggest that stRadC2 may act as an anti-recombination factor in DNA recombinational repair in S. tokodaii
Sequence alignment showed that some of these proteins, for instance, SSO2452 and SSO1861 in S. solfataricus, and ST0579 and ST1830 in S. tokodaii were more similar to the KaiC-like proteins than to any known RadA/Rad51 paralog found throughout archaea and eukarya
Summary
Rad51/RadA paralogs found in eukaryotes and euryarchaea play important roles during recombination and repair, and mutations in one of the human Rad paralogs, Rad51C, are associated with breast and ovarian cancers. No. retardation, increased sensitivity to UV light and recombination defects, suggesting a role of RadB as a recombination mediator [9] The hyperthermophilic crenarchaea, another branch of archaea, has several RadA homologs, such as SSO2452, SSO1861 and SSO0777 in Sulfolobus solfataricus, and ST0579, ST0838, ST1830 and ST2522 in S. tokodaii [12–14]. Sequence alignment showed that some of these proteins, for instance, SSO2452 and SSO1861 in S. solfataricus, and ST0579 and ST1830 in S. tokodaii were more similar to the KaiC-like proteins than to any known RadA/Rad paralog found throughout archaea and eukarya These proteins were named RadC by Haldenby [9]. Further investigations revealed that stRadC2 inhibited RadA-mediated recombination and facilitated the resolution of Holliday junction DNA via Hjc, the Holliday junction endonuclease These results suggest that stRadC2 might work at the late stages of archaeal HR
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