Mutagenic DNA repair in Escherichia coli

Ba, Bridges; Rp, Mottershead

doi:10.1007/bf00277304

Cited by 120 publications

(36 citation statements)

References 24 publications

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“…Echols had originally suggested that pol III core was a component of the mutasome, based primarily on genetic evidence indicating a requirement for pol III in SOS mutagenesis (27,28). We have found, however, that the presence of pol III core is not required for TLS (18,19), and in its presence pol V-catalyzed TLS is inhibited (19).…”

Section: Coping With Dna Damage In E Colimentioning

confidence: 74%

Roles of DNA polymerases V and II in SOS-induced error-prone and error-free repair in Escherichia coli

Pham

Rangarajan

Woodgate

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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DNA polymerase V, composed of a heterotrimer of the DNA damage-inducible UmuC and UmuD 2 proteins, working in conjunction with RecA, single-stranded DNA (ssDNA)-binding protein (SSB), ␤ sliding clamp, and ␥ clamp loading complex, are responsible for most SOS lesion-targeted mutations in Escherichia coli, by catalyzing translesion synthesis (TLS). DNA polymerase II, the product of the damage-inducible polB (dinA ) gene plays a pivotal role in replication-restart, a process that bypasses DNA damage in an error-free manner. Replication-restart takes place almost immediately after the DNA is damaged (Ϸ2 min post-UV irradiation), whereas TLS occurs after pol V is induced Ϸ50 min later. We discuss recent data for pol V-catalyzed TLS and pol II-catalyzed replicationrestart. Specific roles during TLS for pol V and each of its accessory factors have been recently determined. Although the precise molecular mechanism of pol II-dependent replication-restart remains to be elucidated, it has recently been shown to operate in conjunction with RecFOR and PriA proteins.T wo seemingly unconnected questions arising during the early and mid 1970s were to decipher the biochemical basis of SOS mutagenesis in Escherichia coli, often referred to as SOS errorprone repair (1), and to determine a cellular role for E. coli DNA polymerase II. A tentative link between the two was established when it was determined that pol II was induced as part of the LexA-regulon (2). pol II was subsequently shown to be encoded by the DNA damage-inducible polB (dinA) gene (3-5). A ⌬polB strain shows no measurable UV sensitivity, and SOS-induced mutagenesis occurs at normal levels (6, 7). However, a ⌬polB ⌬umuDC double mutant strain is more sensitive to killing by UV light than either of the single mutant strains, implying that the two SOS-induced polymerases might play compensatory roles in vivo (8).The ability of pols II and V to complement each other does not mean that these activities are functionally redundant, and indeed they are not. pol V is able to copy UV-damaged DNA in a process referred to as error-prone translesion synthesis (TLS). TLS generates mutations targeted specifically to DNA template damage sites (9-12). In contrast, pol II copies chromosomal DNA during error-free replication-restart (8). Although both polymerases are induced by DNA damage, they appear to function on widely disparate time frames-pol II-catalyzed replication-restart occurs 2 min post-UV irradiation whereas pol V-catalyzed TLS begins roughly 50 min later (8). In this paper, we discuss current models for the roles of pol V in TLS and pol II in replication-restart.Coping with DNA Damage in E. coli There are over 40 genes induced on DNA damage in E. coli that have been identified recently by using microarray chip technology (13), of which at least 31 are known to be negatively regulated at the transcriptional level by the LexA protein (14). Many of these genes encode proteins required to repair DNA damage (15). The overriding importance of DNA repair is apparent from the ob...

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Section: Coping With Dna Damage In E Colimentioning

confidence: 74%

Roles of DNA polymerases V and II in SOS-induced error-prone and error-free repair in Escherichia coli

Pham

Rangarajan

Woodgate

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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“…Also, it has been observed that a high cellular level of UmuC is exceptionally harmful to the defective DNA polymerase III (pol III) of the dnaQ49 mutant (38). These data suggest that UmuD and UmuC proteins may directly interact with the DNA replication apparatus.Experimental data available to date have suggested the involvement of DNA pol III in the SOS mutagenic pathway (4,17,23,40,41). Recent studies have shown that DNA pol III holoenzyme, in concert with UmuDЈ, UmuC, and RecA proteins, promotes in vitro replication across the site of the DNA lesion (21,40,41).…”

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confidence: 99%

Specific in vivo protein-protein interactions between Escherichia coli SOS mutagenesis proteins

Jonczyk

Nowicka

1996

J Bacteriol

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One of the components of the RecA-LexA-controlled SOS response in Escherichia coli cells is an inducible error-prone DNA replication pathway that results in a substantial increase in the mutation rate. It is believed that error-prone DNA synthesis is performed by a multiprotein complex that is formed by UmuC, UmuD, RecA, and probably DNA polymerase III holoenzyme. It is postulated that the formation of such a complex requires specific interactions between these proteins. We have analyzed the specific protein-protein interactions between UmuC, UmuD, and UmuD fusion proteins, using a Saccharomyces cerevisiae two-hybrid system. In agreement with previous in vitro data, we have shown that UmuD and UmuD are able to form both homodimers (UmuD-UmuD and UmuD-UmuD) and a heterodimer (UmuD-UmuD). Our data show that UmuC fusion protein is capable of interacting exclusively with UmuD and not with UmuD. Thus, posttranslational processing of UmuD into UmuD is a critical step in SOS mutagenesis, enabling only the latter protein to interact with UmuC. Our data seem to indicate that the integrity of the entire UmuC sequence is essential for UmuC-UmuD heterotypic interaction. Finally, in our studies, we used three different UmuC mutant proteins: UmuC25, UmuC36, and UmuC104. We have found that UmuC25 and UmuC36 are not capable of associating with UmuD. In contrast, UmuC104 protein interacts with UmuD protein with an efficiency identical to that of the wild-type protein. We postulate that UmuC104 protein might be defective in interaction with another, unknown protein essential for the SOS mutagenesis pathway.Exposure of Escherichia coli cells to agents that damage DNA and introduce replication-blocking lesions results in the induction of the SOS regulon (13,22,33,51,52). Approximately 20 cellular genes are derepressed when activated RecA promotes the proteolytic cleavage of LexA protein, the repressor of SOS genes (22,25,32,33,44,51,52).One of the components of the RecA-LexA-controlled SOS response is an inducible error-prone DNA replication pathway that causes a significant increase in the mutation rate (13,22,33,51,52). Genetic and physiological experiments indicate that the products of the umuDC operon and the recA gene are essential components of the SOS mutation pathway (3,12,16,17,26,44,47,48). This is supported by the fact that umuD and umuC mutants of E. coli are virtually nonmutable with UV light and many chemical agents (26,47).The recA and umuDC genes are members of the SOS regulon and are expressed at elevated levels after DNA damage (15,31,46,53,55). In SOS-competent cells, activated RecA also mediates the cleavage of UmuD at its Cys-24-Gly-25 bond, yielding a shorter UmuDЈ product, which has been proposed to be an active form of UmuD for mutagenesis (6,37,45,54). Several data suggest that UmuC, UmuDЈ, and RecA proteins facilitate the proceeding of the DNA replication complex beyond lesions in the template (5, 21, 40, 41). In addition, it has been shown that overexpression of the umuDC operon results in cold sensitivit...

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“…1 and Table 1). Therefore, all we have learned about DNA synthesis by DNA polymerase I on irradiated template may also apply to DNA polymerase III,t which is more likely to be involved in UVinduced mutagenesis (28).…”

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confidence: 99%

Mechanism of ultraviolet-induced mutagenesis: Extent and fidelity of in vitro DNA synthesis on irradiated templates

Villani

Boiteux

Radman

1978

Proc. Natl. Acad. Sci. U.S.A.

147

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The effect of UV irradiation on the extent and fidelity of DNA synthesis in vitro was studied by using homopolymers and primed single-stranded kX174 phage DNA polymerase I on irradiated 4X174 DNA has been observed. We propose that this nucleotide turnover is due to idling by DNA polymerase (i.e., incorporation and subsequent excision of nucleotides opposite UV photolesions, by the 3'_-5' "proofreading" exonuclease) thus preventing replication past pyrimidine dimers and the potentially mutagenic event that should result. In support of this hypothesis, DNA synthesis by DNA polymerase from avian myeloblastosis virus and by mammalian DNA polymerase a, both of which are devoid of any exonuclease activity, was found to be only partially inhibited, but not blocked, by UV irradiation of the template and accompanied by an increased incorporation of noncomplementary nucleotides. It is suggested that UV mutagenesis inbacteria requires an induced modification of the cellular DNA replication machinery, possibly an inhibition of the 3'-5' exonuclease activity associated with DNA polymerases.UV irradiation of X and 4X174 bacteriophages results in killing, but not mutagenesis, of phage after infection of untreated host cells (1, 2), whereas UV irradiation of the host cells causes mutagenesis of both untreated and irradiated phage (1-4).Furthermore, UV-irradiated single-stranded qX174 DNA extracted from untreated host cells was found to be replicated only to the first pyrimidine dimer (5, 6). Caillet-Fauquet et al. (6) found that UV irradiation of the host cell leads to an enhancement of the DNA synthesis on UV-irradiated OX174 DNA in vivo, which led them to propose that pyrimidine dimers in the cX174 DNA can become mutagenic by causing misincorporation of deoxyribonucleotides opposite them.This inducible mutagenic system is thought to be part of a complex cellular emergency response ("SOS induction") that is triggered by unrepaired DNA lesions (such as pyrimidine dimers). The response also includes the arrest of cellular division, the arrest of aerobic metabolism, and the induction of prophage in lysogenic bacteria (7,8).DNA polymerases (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) are known to be able to control the fidelity of DNA synthesis by selection of the correct nucleotide (9) and by possession of a "proof-reading" 3'-"5' exonuclease activity that can detect and excise 3'-terminal mismatched bases (10, 11).We have sought to understand the molecular mechanisms underlying UV-induced mutagenesis by an examination of the role of DNA

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Mutagenic DNA repair in Escherichia coli

Cited by 120 publications

References 24 publications

Roles of DNA polymerases V and II in SOS-induced error-prone and error-free repair in Escherichia coli

Roles of DNA polymerases V and II in SOS-induced error-prone and error-free repair in Escherichia coli

Specific in vivo protein-protein interactions between Escherichia coli SOS mutagenesis proteins

Mechanism of ultraviolet-induced mutagenesis: Extent and fidelity of in vitro DNA synthesis on irradiated templates

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