Exposure of Sulfolobus solfataricus to the DNA damaging agents
UV-irradiation,
bleomycin or
mitomycin C induces cellular aggregation.[9] Other physical stressors, such as pH or temperature shift, do not induce aggregation, suggesting that induction of aggregation is caused specifically by DNA damage. Ajon et al.[10] showed that UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency. Recombination rates exceeded those of uninduced cultures by up to three orders of magnitude. Frols et al.[9][11] and Ajon et al.[10] hypothesized that the UV-inducible DNA transfer process and subsequent
homologous recombinational repair represents an important mechanism to maintain chromosome integrity. This response may be a primitive form of sexual interaction, similar to the more well-studied bacterial transformation that is also associated with DNA transfer between cells leading to homologous recombinational repair of DNA damage.[citation needed] In another related species, Sulfolobus acidocaldarius, UV-irradiation also increases the frequency of recombination due to genetic exchange.[12]
The ups operon
This section is missing information about illustration of ups organization (with UniProt IDs). Please expand the section to include this information. Further details may exist on the
talk page.(May 2020)
The ups (UV-induced pilus) operon of Sulfolobus species is highly induced by UV irradiation. The
pili encoded by this operon are employed in promoting cellular aggregation, which is necessary for subsequent DNA exchange between cells, resulting in
homologous recombination.[13]
A study of the Sulfolobales acidocaldarius ups operon showed that one of the genes downstream of the operon, saci-1497, encodes an
endonuclease III that nicks UV-damaged DNA; and another gene of the operon, saci-1500, encodes a
RecQ-like helicase that is able to unwind homologous recombination intermediates such as
Holliday junctions.[13] It was proposed that Saci-1497 and Saci-1500 function in an homologous recombination-based DNA repair mechanism that uses transferred DNA as a template.[13] Thus it is thought that the ups system in combination with homologous recombination provide a DNA damage response which rescues Sulfolobales from DNA damaging threats.[13]
^Fröls S, White MF, Schleper C (2009). "Reactions to UV damage in the model archaeon Sulfolobus solfataricus". Biochem. Soc. Trans. 37 (Pt 1): 36–41.
doi:
10.1042/BST0370036.
PMID19143598.
Stetter, KO (1989). "Order III. Sulfolobales ord. nov. Family Sulfolobaceae fam. nov.". In JT Staley; MP Bryant; N Pfennig; JG Holt (eds.). Bergey's Manual of Systematic Bacteriology. Vol. 3 (1st ed.). Baltimore: The Williams & Wilkins Co. p. 169.