Humans have at least four members of this superfamily. For brevity, we will refer to it as the UmuC superfamily because UmuC was its founding member ( 9, 10, 27, 28). coli members, UmuC and DinB, and the two Saccharomyces cerevisiae members, Rad30p and Rev1p, define its four subfamilies. These newly discovered DNA polymerases contain highly conserved blocks of amino acid sequences ( 26) and constitute a new superfamily of novel DNA polymerases termed the UmuC-DinB-Rad30-Rev1 superfamily because the two E. Depending on the DNA polymerase, these include templates such as those containing a misaligned primer–template junction ( 13), an abasic site ( 6, 7), a cyclobutane dimer ( 15, 16, 25), or a pyrimidine–pyrimidone ( 6– 4) photoproduct ( 25). A common, defining feature of these DNA polymerases is a remarkable ability to replicate imperfect DNA templates. Recently, the field of translesion DNA synthesis and induced mutagenesis has generated a great deal of excitement because of the discovery that key gene products required for these processes, in both prokaryotes ( 9, 10) and in eukaryotes ( 11, 12), possess an intrinsic DNA polymerase activity (refs. In particular, we discuss these issues in the context of the Gram-negative bacterium, Escherichia coli, that contains a DNA polymerase (Pol V) known to participate in most, if not all, of these processes. Here, we have attempted to summarize our current understanding of the regulation of action of DNA polymerases with respect to their roles in DNA replication, TLS, DNA repair, DNA recombination, and cell cycle progression. Members of this family have recently received a great deal of attention due to the roles they play in translesion DNA synthesis (TLS), the potentially mutagenic replication over DNA lesions that act as potent blocks to continued replication catalyzed by replicative DNA polymerases. This UmuC-DinB-Rad30-Rev1 superfamily of DNA polymerases has members in all three kingdoms of life. Most notably, the current list now includes a completely new family of enzymes that are capable of replicating imperfect DNA templates. Two important and timely questions with respect to DNA replication, DNA recombination, and DNA repair are: ( i) what controls which DNA polymerase gains access to a particular primer-terminus, and ( ii) what determines whether a DNA polymerase hands off its DNA substrate to either a different DNA polymerase or to a different protein(s) for the completion of the specific biological process? These questions have taken on added importance in light of the fact that the number of known template-dependent DNA polymerases in both eukaryotes and in prokaryotes has grown tremendously in the past two years. Genetic and Biochemical Evidence Suggesting a Need for Multiple DNA Polymerases for Bypassing Certain DNA Lesions.The β Processivity Clamp of Pol III Communicates Directly with Multiple Proteins to Promote DNA Replication and DNA Repair. Interactions with Components of the Replicative DNA Polymerase Appear to Play a Role in TLS and Checkpoint Functions of the umuDC Gene Products.A DNA Polymerase Protein Can Have Additional Biological Roles.Translesion Synthesis by DNA Pol V also Requires RecA and SSB.coli DNA Polymerase V ( umuDC) Is Regulated both Transcriptionally and Posttranslationally. coli DNA Polymerase V ( umuDC): Lessons Learned from More than 25 Years of Studying a Lesion-Bypass DNA Polymerase. Other Physiological Roles of DNA Polymerases Besides Chromosomal DNA Replication.
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