期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1998
卷号：95
期号：26
页码：15519-15524
DOI：10.1073/pnas.95.26.15519
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Translesion replication (TR) past a cyclobutane pyrimidine dimer in Escherichia coli normally requires the UmuD'2C complex, RecA protein, and DNA polymerase III holoenzyme (pol III). However, we find that efficient TR can occur in the absence of the Umu proteins if the 3'-5' exonuclease proofreading activity of the pol III {varepsilon}-subunit also is disabled. TR was measured in isogenic uvrA6 {Delta}umuDC strains carrying the dominant negative dnaQ allele, mutD5, or {Delta}dnaQ spq-2 mutations by transfecting them with single-stranded M13-based vectors containing a specifically located cis-syn T-T dimer. As expected, little TR was observed in the {Delta}umuDC dnaQ+ strain. Surprisingly, 26% TR occurred in UV-irradiated {Delta}umuDC mutD5 cells, one-half the frequency found in a uvrA6 umuDC+mutD5 strain. lexA3 (Ind-) derivatives of the strains showed that this TR was contingent on two inducible functions, one LexA-dependent, responsible for {approx}70% of the TR, and another LexA-independent, responsible for the remaining {approx}30%. Curiously, the {Delta}umuDC {Delta}dnaQ spq-2 strain exhibited only the LexA-independent level of TR. The cause of this result appears to be the spq-2 allele, a dnaE mutation required for viability in {Delta}dnaQ strains, since introduction of spq-2 into the {Delta}umuDC mutD5 strain also reduces the frequency of TR to the LexA-independent level. The molecular mechanism responsible for the LexA-independent TR is unknown but may be related to the UVM phenomenon [Palejwala, V. A., Wang, G. E., Murphy, H. S. & Humayun, M. Z. (1995) J. Bacteriol. 177, 6041-6048]. LexA-dependent TR does not result from the induction of pol II, since TR in the {Delta}umuDC mutD5 strain is unchanged by introduction of a {Delta}polB mutation.
