Repair of DNA Double-Strand Breaks following UV Damage in Three Sulfolobus solfataricus Strains

DNA damage repair mechanisms have been most thoroughly explored in the eubacterial and eukaryotic branches of life. The methods by which members of the archaeal branch repair DNA are significantly less well understood but have been gaining increasing attention. In particular, the approaches employed by hyperthermophilic archaea have been a general source of interest, since these organisms thrive under conditions that likely lead to constant chromosomal damage. In this work we have characterized the responses of three Sulfolobus solfataricus strains to UV-C irradiation, which often results in double-strand break formation. We examined S. solfataricus strain P2 obtained from two different sources and S. solfataricus strain 98/2, a popular strain for site-directed mutation by homologous recombination. Cellular recovery, as determined by survival curves and the ability to return to growth after irradiation, was found to be strain specific and differed depending on the dose applied. Chromosomal damage was directly visualized using pulsed-field gel electrophoresis and demonstrated repair rate variations among the strains following UV-C irradiation-induced double-strand breaks. Several genes involved in double-strand break repair were found to be significantly upregulated after UV-C irradiation. Transcript abundance levels and temporal expression patterns for double-strand break repair genes were also distinct for each strain, indicating that these Sulfolobus solfataricus strains have differential responses to UV-C-induced DNA double-strand break damage.