Polymorphism of genes encoding SOS polymerases in natural populations of Escherichia coli.
High fidelity replicative DNA polymerases can be blocked during DNA replication by various base damages, which represents a potentially lethal event. Escherichia coli possesses three DNA polymerases, PolII, PolIV and PolV, that can continue replication over such lesions in template DNA, thus allowing for cell survival. Genes coding for these enzymes, polB, dinB, and umuCD respectively, belong to the stress-inducible SOS regulon. We have analyzed the patterns of nucleotide sequence variability of genes encoding for three SOS polymerases from E. coli natural isolates in order to identify the nature of selective forces that determine their evolution. The frequency of inferred inter-strain recombination events, and the frequency of synonymous and non-synonymous base substitutions within these genes do not deviate significantly from those observed for the control group composed of 2 genes coding for DNA polymerases PolI and PolIII and 10 metabolic genes. This suggests that the loci coding for SOS polymerases are subject to selective pressure for the maintenance of their function and specificity. The fact that genes coding for translesion-synthesis (TLS) polymerases, particularly dinB and umuC homologs, have been conserved during evolution and the present analysis suggest that their activity is essential for the cellular survival and fitness.
Bjedov
Ivana
I
INSERM U571, Faculté de Médecine Necker-Enfants Malades, Université Paris V, 156 rue Vaugirard, France.
Lecointre
Guillaume
G
Tenaillon
Olivier
O
Vaury
Christelle
C
Radman
Miroslav
M
Taddei
François
F
Denamur
Erick
E
Matic
Ivan
I
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003062:Codon; D004256:DNA Polymerase I / Q000235:genetics* / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D011110:Polymorphism, Genetic; D012641:Selection, Genetic
D001426:Bacterial Proteins; D003062:Codon; C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; C074431:polB protein, E coli; C078202:UmuC protein, E coli; D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase