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. 1999 Oct 26;96(22):12224-6.
doi: 10.1073/pnas.96.22.12224.

Bridging the gap: a family of novel DNA polymerases that replicate faulty DNA

R E Johnson, M T Washington, S Prakash, L Prakash

Bridging the gap: a family of novel DNA polymerases that replicate faulty DNA

R E Johnson et al. Proc Natl Acad Sci U S A. .
No abstract available

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Figures

Figure 1
Figure 1
Modes of bypass replication in E. coli and S. cerevisiae. As DNA replication proceeds, the replicative DNA polymerases, PolIII in E. coli or Polδ in S. cerevisiae, encounter lesions or stall sites (triangles) in DNA. In E. coli, the DNA polymerase activity of the UmuD′2C complex carries out limited DNA synthesis across and past the lesion in an error-prone manner. At replicative pause sites, such as at a misaligned template-primer junction, the DinB protein could carry out limited synthesis, resulting in −1 frameshifts. In S. cerevisiae, the RAD30-encoded Polη performs replicative bypass of thymine dimers in an error-free manner by the insertion of two adenines across from the dimer. Alternatively, the Rev1 protein together with the REV3/REV7-encoded Polζ carries out replicative bypass of UV lesions and other base damages in an error-prone manner. In humans, defects in Polη in XP-V patients result in the loss of this error-free component of UV damage bypass. Elevated mutagenesis arising from increased bypass by Polζ would be the underlying cause of high cancer incidence in XP-V patients.
Figure 2
Figure 2
Schematic alignment of DinB/UmuC/Rad30 family proteins. Boxes represent amino acid sequences of the proteins. Regions of homology are indicated by colored larger boxes, whereas unique sequences are shown as narrow white boxes. Areas without boxes indicate gaps introduced for optimal alignment. Motifs I-III are shown with their respective consensus sequences where x indicates any amino acid and + indicates a hydrophobic residue (I, L, or V). Motifs IV and V represent the helix–hairpin–helix (HhH) domains. The HhH2 sequence in the hRad30A family, indicated in hatched red, differs from the analogous sequence present in the other proteins, indicated in solid red. The DinB-specific sequences are indicated by x, y and z. Zinc binding motifs are indicated as C2H2 or C2HC. Numbers in parentheses indicate protein length in amino acids. Sc, S. cerevisiae; SP, S. pombe; h, human; Ec, E. coli; Ce, C. elegans; BRCT, BRCA1 C-terminal domain. The asterisks on Ce F22B7.6 and Sp SPCC5533.07C indicate that these protein sequences were derived from the alternate predicted mRNA splice sites in the 3′ regions of these genes that would produce a longer protein. Alignments were generated by using the macaw and clustal w programs.
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