DNA Repair and DNA Damage Tolerance in Archaeal Bacteria: Extreme Environments and Genome Integrity
Takehiko Nohmi, Masami Yamada and Petr Gruz
from: Archaea: New Models for Prokaryotic Biology (Edited by: Paul Blum). Caister Academic Press, U.K. (2008)
Maintenance of genome integrity is a mechanism central to cellular life. Many Archaeal species live in harsh habitats that are extreme challenges to genome stability. In the habitat at high ambient temperatures, deamination, oxidation and depurination are greatly accelerated and various lesions are supposed to accumulate in the genomic DNA. Thus, the organisms living in such extreme conditions seem to evolve novel strategies for repairing DNA damage and avoiding mutations caused by the lesions. In this chapter, we review mechanisms of DNA repair in archaeal bacteria and unique properties of archaeal DNA polymerases (Pols) to tolerate DNA damage. In general, archaeal DNA repair proteins are eukaryote-like although many counterparts are missing in the genome sequences. Archaeal B-family DNA Pols, such as Sso DNA Pol B1 or Pfu, halt DNA replication several base pairs before template uracil or hypoxanthine, deamination products of cytosine or adenine in template DNA, respectively, thereby apparently avoiding mutations (read-ahead mechanism). Fifteen out of 38 archaeal species whose genome sequences have been completely determined seem to possess Y-family DNA Pols, which are specialized to bypass lesions in DNA. Collectively, these molecular features warrant the future investigation on how Archaea accommodate DNA damage inevitably occurring in the extreme harsh environments read more ...