The mechanism of recA polA lethality: suppression by RecA-independent recombination repair activated by the lexA(Def) mutation in Escherichia coli.

Abstract The mechanism of recA polA lethality in Escherichia coli has been studied. Complementation tests have indicated that both the 5'-->3' exonuclease and the polymerization activities of DNA polymerase I are essential for viability in the absence of RecA protein, whereas the viability and DNA replication of DNA polymerase I-defective cells depend on the recombinase activity of RecA. An alkaline sucrose gradient sedimentation analysis has indicated that RecA has only a minor role in Okazaki fragment processing. Double-strand break repair is proposed for the major role of RecA in the absence of DNA polymerase I. The lexA(Def)::Tn5 mutation has previously been shown to suppress the temperature-sensitive growth of recA200(Ts) polA25::spc mutants. The lexA(Def) mutation can alleviate impaired DNA synthesis in the recA200(Ts) polA25::spc mutant cells at the restrictive temperature. recF+ is essential for this suppression pathway. recJ and recQ mutations have minor but significant adverse effects on the suppression. The recA200(Ts) allele in the recA200(Ts) polA25::spc lexA(Def) mutant can be replaced by delta recA, indicating that the lexA(Def)-induced suppression is RecA independent. lexA(Def) reduces the sensitivity of delta recA polA25::spc cells to UV damage by approximately 10(4)-fold. lexA(Def) also restores P1 transduction proficiency to the delta recA polA25::spc mutant to a level that is 7.3% of the recA+ wild type. These results suggest that lexA(Def) activates a RecA-independent, RecF-dependent recombination repair pathway that suppresses the defect in DNA replication in recA polA double mutants.

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DNA polymerase I and the bypassing of RecA dependence of constitutive stable DNA replication in Escherichia coli rnhA mutants.

Journal of Bacteriology ◽

10.1128/jb.175.22.7247-7253.1993 ◽

1993 ◽

Vol 175 (22) ◽

pp. 7247-7253 ◽

Cited By ~ 3

Author(s):

Y Cao ◽

R R Rowland ◽

T Kogoma

Keyword(s):

Escherichia Coli ◽

Dna Replication ◽

Dna Polymerase ◽

Dna Polymerase I ◽

Stable Dna Replication ◽

Polymerase I

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Interaction between the plasmid R6K andEscherichia coliwith defective DNA polymerase I

Genetics Research ◽

10.1017/s0016672300018498 ◽

1978 ◽

Vol 32 (1) ◽

pp. 25-35 ◽

Cited By ~ 1

Author(s):

D. J. Tweats ◽

J. T. Smith

Keyword(s):

Cell Division ◽

Dna Polymerase ◽

Temperature Sensitive ◽

Restrictive Temperature ◽

Dna Polymerase I ◽

E Coli ◽

R Factor ◽

Polymerase I

SUMMARYInitial experiments demonstrated that the plasmid R6K cannot be transferred to or maintained readily in theE. coliDNA polymerase I deficient strain JG138polA1. Results withE. coliMM386polA12(R6K), which has a temperature sensitive polymerase I enzyme, showed cell division becomes abnormal when the polymerase I enzyme of the host bacteria is inactivated at the restrictive temperature. Under conditions of polymerase I deficiency, R6K replication, as measured by monitoring R-factor-mediated β-lactamase activity, also becomes abnormal with the loss of multiple R6K copies per cell and the apparent maintenance of a single R-factor copy per cell.

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DNA polymerase I is required for premeiotic DNA replication and sporulation but not for X-ray repair in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.9.2.365-376.1989 ◽

1989 ◽

Vol 9 (2) ◽

pp. 365-376

Author(s):

M E Budd ◽

K D Wittrup ◽

J E Bailey ◽

J L Campbell

Keyword(s):

Saccharomyces Cerevisiae ◽

Dna Replication ◽

Dna Polymerase ◽

Temperature Sensitive ◽

Dna Polymerase I ◽

X Ray ◽

Temperature Sensitive Mutants ◽

Polymerase I ◽

Dna Polymerase Ii

We have used a set of seven temperature-sensitive mutants in the DNA polymerase I gene of Saccharomyces cerevisiae to investigate the role of DNA polymerase I in various aspects of DNA synthesis in vivo. Previously, we showed that DNA polymerase I is required for mitotic DNA replication. Here we extend our studies to several stages of meiosis and repair of X-ray-induced damage. We find that sporulation is blocked in all of the DNA polymerase temperature-sensitive mutants and that premeiotic DNA replication does not occur. Commitment to meiotic recombination is only 2% of wild-type levels. Thus, DNA polymerase I is essential for these steps. However, repair of X-ray-induced single-strand breaks is not defective in the DNA polymerase temperature-sensitive mutants, and DNA polymerase I is therefore not essential for repair of such lesions. These results suggest that DNA polymerase II or III or both, the two other nuclear yeast DNA polymerases for which roles have not yet been established, carry out repair in the absence of DNA polymerase I, but that DNA polymerase II and III cannot compensate for loss of DNA polymerase I in meiotic replication and recombination. These results do not, however, rule out essential roles for DNA polymerase II or III or both in addition to that for DNA polymerase I.

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