title: Lyase activities intrinsic to Escherichia coli polymerases IV and V.
abstract: Escherichia coli DNA polymerase IV and V (pol IV and pol V) are error-prone DNA polymerases that are induced as part of the SOS regulon in response to DNA damage. Both are members of the Y-family of DNA polymerases. Their principal biological roles appear to involve translesion synthesis (TLS) and the generation of mutational diversity to cope with stress. Although neither enzyme is known to be involved in base excision repair (BER), we have nevertheless observed apurinic/apyrimidinic 5'-deoxyribose phosphate (AP/5'-dRP) lyase activities intrinsic to each polymerase. Pols IV and V catalyze cleavage of the phosphodiester backbone at the 3'-side of an apurinic/apyrimidinic (AP) site as well as the removal of a 5'-deoxyribose phosphate (dRP) at a preincised AP site. The specific activities of the two error-prone polymerase-associated lyases are approximately 80-fold less than the associated lyase activity of human DNA polymerase beta, which is a key enzyme used in short patch BER. Pol IV forms a covalent Schiff's base intermediate with substrate DNA that is trapped by sodium borohydride, as proscribed by a beta-elimination mechanism. In contrast, a NaBH(4) trapped intermediate is not observed for pol V, even though the lyase specific activity of pol V is slightly higher than that of pol IV. Incubation of pol V (UmuD'(2)C) with a molar excess of UmuD drives an exchange of subunits to form UmuD'D+insoluble UmuC causing inactivation of polymerase and lyase activities. The concomitant loss of both activities is strong evidence that pol V contains a bona fide lyase activity.
authors.affiliation: Department of Biological Sciences and Chemistry, Hedco Molecular Biology Laboratories, University of Southern California, University Park, Los Angeles, 90089-1340, USA.
authors.forename: Xuan
authors.initials: X
authors.lastname: Shen
authors.forename: Roger
authors.initials: R
authors.lastname: Woodgate
authors.forename: Myron F
authors.initials: MF
authors.lastname: Goodman
mesh_terms: D000595:Amino Acid Sequence; D001894:Borohydrides / Q000737:chemistry; D004247:DNA / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D019951:DNA Polymerase beta / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D019384:Nucleic Acid Synthesis Inhibitors; D016415:Sequence Alignment
chemical_list: D001894:Borohydrides; D029968:Escherichia coli Proteins; D019384:Nucleic Acid Synthesis Inhibitors; C025364:sodium borohydride; D004247:DNA; D019951:DNA Polymerase beta; C120926:DNA polymerase V, E coli; D004259:DNA-Directed DNA Polymerase; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase