Molecular and General Genetics MGG

, Volume 251, Issue 4, pp 493–498 | Cite as

Analysis of the mutagenic properties of the UmuDC, MucAB and RumAB proteins, using a site-specific abasic lesion

  • C. W. Lawrence
  • A. Borden
  • R. Woodgate
Original Paper


ThemucAB andrumAB loci have been shown to promote mutagenesis to a greater extent than the structurally and functionally homologousEscherichia coli umuDC operon. We have analyzed the basis of this enhanced mutagenesis by comparing the influence of these operons, relative toumuDC, on the mutagenic properties of each of two abasic sites, specifically located in a single-stranded vector. Experiments with these vectors are useful analytical tools because they provide independent estimates of the efficiency of translesion synthesis and of the relative frequencies of each type of nucleotide insertion or other kind of mutagenic event. TheumuDC, mucAB, andrumAB genes were expressed from their naturalLexA-regulated promoter on low-copy-number plasmids in isogenic strains carrying aumuDC deletion. In addition, plasmids expressing the UmuD'C, MucA'B, or RumA'B proteins were also used. Compared toumuDC, the chief effect ofmucAB was to increase the efficiency of translesion synthesis past the abasic site. The enhanced capacity ofmucAB for translesion synthesis depended about equally on an inherently greater capacity to promote this process and on a greater susceptibility of the MucA protein to proteolytic processing. The RumA protein also appeared to be more susceptible to proteolytic processing, but the inherent capacity of theRum products for translesion synthesis was no greater than that ofUmuDC. dAMP was inserted opposite one of the two abasic sites studied at a somewhat greater frequency in strains expressingrum (82%) compared to those expressingumu (72%), which might result in higher mutation frequencies inrumAB than inumuDC strains.

Key words

Escherichia coli umuDC mucAB rumAB Specifically located abasic site 


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • C. W. Lawrence
    • 1
  • A. Borden
    • 1
  • R. Woodgate
    • 2
  1. 1.Department of BiophysicsUniversity of Rochester Medical CenterRochesterUSA
  2. 2.Section on DNA Replication, Repair and Mutagenesis, National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaUSA

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