RecA-mediated cleavage activates UmuD for mutagenesis: mechanistic relationship between transcriptional derepression and posttranslational activation.

Nohmi, Takehiko; Battista, John R.; Dodson, Lori A.; Walker, Graham C.

doi:10.1073/pnas.85.6.1816

Cited by 351 publications

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“…UmuD initially causes a pause in cell division while DNA repair and replication occurs (Opperman et al, 1999). However, within minutes, UmuD homodimerizes and carries out intermolecular self-cleavage, facilitated by activated RecA* interaction (Nohmi et al, 1988). Two cleaved UmuD9 molecules then associate with UmuC to form DNA polymerase V, which carries out error-prone, trans-lesion DNA replication (SOS mutagenesis) (Reuven et al, 1999;Tang et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Diverse responses to UV light exposure in Acinetobacter include the capacity for DNA damage-induced mutagenesis in the opportunistic pathogens Acinetobacter baumannii and Acinetobacter ursingii

et al. 2012

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Error-prone and error-free DNA damage repair responses that are induced in most bacteria after exposure to various chemicals, antibiotics or radiation sources were surveyed across the genus Acinetobacter. The error-prone SOS mutagenesis response occurs when DNA damage induces a cell's umuDC-or dinP-encoded error-prone polymerases. The model strain Acinetobacter baylyi ADP1 possesses an unusual, regulatory umuD allele (umuDAb) with an extended 59 region and only incomplete fragments of umuC. Diverse Acinetobacter species were investigated for the presence of umuDC and their ability to conduct UV-induced mutagenesis. Unlike ADP1, most Acinetobacter strains possessed multiple umuDC loci containing either umuDAb or a umuD allele resembling that of Escherichia coli. The nearly omnipresent umuDAb allele was the ancestral umuD in Acinetobacter, with horizontal gene transfer accounting for over half of the umuDC operons. Despite multiple umuD(Ab)C operons in many strains, only three species conducted UV-induced mutagenesis: Acinetobacter baumannii, Acinetobacter ursingii and Acinetobacter beijerinckii. The type of umuDC locus or mutagenesis phenotype a strain possessed was not correlated with its error-free response of survival after UV exposure, but similar diversity was apparent. The survival of 30 Acinetobacter strains after UV treatment ranged over five orders of magnitude, with the Acinetobacter calcoaceticus-A. baumannii (Acb) complex and haemolytic strains having lower survival than non-Acb or non-haemolytic strains. These observations demonstrate that a genus can possess a range of DNA damage response mechanisms, and suggest that DNA damage-induced mutation could be an important part of the evolution of the emerging pathogens A. baumannii and A. ursingii. INTRODUCTIONWhen bacteria are exposed to DNA-damaging agents, such as UV light or chemical mutagens, a wide variety of SOS response genes (genes that play critical roles in repairing damaged DNA) are specifically induced (Friedberg et al., 1995;Walker, 1996). In the model developed by experimentation in Escherichia coli, SOS genes are negatively regulated by the LexA repressor binding to the SOS box in the promoter (Mount et al., 1972). DNA damage causes the activation of RecA, which facilitates LexA self-cleavage and releases the repression of SOS genes such as umuDC (Little et al., 1980;1981). UmuD initially causes a pause in cell division while DNA repair and replication occurs (Opperman et al., 1999). However, within minutes, UmuD homodimerizes and carries out intermolecular self-cleavage, facilitated by activated RecA* interaction (Nohmi et al., 1988). Two cleaved UmuD9 molecules then associate with UmuC to form DNA polymerase V, which carries out error-prone, trans-lesion DNA replication (SOS mutagenesis) (Reuven et al., 1999;Tang et al., 1999). Another errorprone polymerase commonly involved in SOS mutagenesis as part of the DNA damage response is DinP (also called DinB), DNA polymerase IV, which can function either by itself (Kim et al., 1997) or with U...

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Section: Introductionmentioning

confidence: 99%

Diverse responses to UV light exposure in Acinetobacter include the capacity for DNA damage-induced mutagenesis in the opportunistic pathogens Acinetobacter baumannii and Acinetobacter ursingii

et al. 2012

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“…Both proteins have been shown to interact with UmuC (5), DinB (the Y family DNA Pol IV) (7), and three subunits of the replicative DNA Pol III (8). Additionally, both interact with RecA:ssDNA nucleoprotein filaments (3,9).…”

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“…The initial product, UmuD 2 , is a homodimer composed of 139 amino acid subunits that appears early after SOS induction (2). Damage-induced RecA:ssDNA nucleoprotein filaments mediate a slow autocleavage of UmuD 2 that is mechanistically similar to the inactivation of the LexA repressor (3). The N-terminal 24 amino acids of each subunit of UmuD 2 are removed, leaving a homodimer of the C-terminal 115 amino acid subunits, UmuDЈ 2 (3).…”

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Regulation of Escherichia coli SOS mutagenesis by dimeric intrinsically disordered umuD gene products

Simon

Sousa²,

Mohana‐Borges³

et al. 2008

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

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Products of the umuD gene in Escherichia coli play key roles in coordinating the switch from accurate DNA repair to mutagenic translesion DNA synthesis (TLS) during the SOS response to DNA damage. Homodimeric UmuD 2 is up-regulated 10-fold immediately after damage, after which slow autocleavage removes the Nterminal 24 amino acids of each UmuD. The remaining fragment, UmuD 2, is required for mutagenic TLS. The small proteins UmuD2 and UmuD 2 make a large number of specific protein-protein contacts, including three of the five known E. coli DNA polymerases, parts of the replication machinery, and RecA recombinase. We show that, despite forming stable homodimers, UmuD 2 and UmuD 2 have circular dichroism (CD) spectra with almost no ␣-helix or ␤-sheet signal at physiological concentrations in vitro. High protein concentrations, osmolytic crowding agents, and specific interactions with a partner protein can produce CD spectra that resemble the expected ␤-sheet signature. A lack of secondary structure in vitro is characteristic of intrinsically disordered proteins (IDPs), many of which act as regulators. A stable homodimer that lacks significant secondary structure is unusual but not unprecedented. Furthermore, previous single-cysteine cross-linking studies of UmuD 2 and UmuD 2 show that they have a nonrandom structure at physiologically relevant concentrations in vitro. Our results offer insights into structural characteristics of relatively poorly understood IDPs and provide a model for how the umuD gene products can regulate diverse aspects of the bacterial SOS response.natively unfolded ͉ SOS response ͉ unstructured ͉ denatured ͉ DNA repair

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“…Furthermore, RecA mediates the processing of UmuD to a shorter but mutagenically active form, UmuD' (8,40,46). Mutants of umuD or recA that are unable to promote cleavage are rendered phenotypically nonmutable (2,18,31,46).…”

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Isolation and characterization of novel plasmid-encoded umuC mutants

Woodgate¹,

Singh²,

Kulaeva³

et al. 1994

J Bacteriol

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Interestingly, these plasmid mutants fell into two classes: (i) 5 were expression mutants that produced either too little or too much wild-type UmuC protein, and (ii) 11 were plasmids with structural changes in the UmuC protein. Although hydroxylamine mutagenesis was random, most of the structural mutants identified in the screen were localized to two regions of the UmuC protein; four mutations were found in a stretch of 30 amino acids (residues 133 to 162) in the middle of the protein, while four other mutations (three of which resulted in a truncated UmuC protein) were localized in the last 50 carboxyl-terminal amino acid residues. These new plasmid umuC mutants, together with the previously identified chromosomal umuC25, umuC36, and umuC104 mutations that we have also cloned, should prove extremel useful in dissecting the genetic and biochemical activities of UmuC in mutagenic DNA repair.

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RecA-mediated cleavage activates UmuD for mutagenesis: mechanistic relationship between transcriptional derepression and posttranslational activation.

Cited by 351 publications

References 44 publications

Diverse responses to UV light exposure in Acinetobacter include the capacity for DNA damage-induced mutagenesis in the opportunistic pathogens Acinetobacter baumannii and Acinetobacter ursingii

Diverse responses to UV light exposure in Acinetobacter include the capacity for DNA damage-induced mutagenesis in the opportunistic pathogens Acinetobacter baumannii and Acinetobacter ursingii

Regulation of Escherichia coli SOS mutagenesis by dimeric intrinsically disordered umuD gene products

Isolation and characterization of novel plasmid-encoded umuC mutants

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