The mutA mistranslator tRNA-induced mutator phenotype requires recA and recB genes, but not the derepression of lexA-regulated functions.

TitleThe mutA mistranslator tRNA-induced mutator phenotype requires recA and recB genes, but not the derepression of lexA-regulated functions.
Publication TypeJournal Article
Year of Publication1999
AuthorsRen, L, Mamun, AA al, Humayun, MZ
JournalMol Microbiol
Volume32
Issue3
Pagination607-15
Date Published1999 May
ISSN0950-382X
KeywordsAlleles, Aspartic Acid, Bacterial Proteins, Base Sequence, Escherichia coli, Escherichia coli Proteins, Exodeoxyribonuclease V, Exodeoxyribonucleases, Gene Expression Regulation, Bacterial, Glycine, Molecular Sequence Data, Mutation, Phenotype, Protein Biosynthesis, Rec A Recombinases, RNA, Transfer, Gly, Serine Endopeptidases, SOS Response (Genetics)
Abstract

The mapping of mutA and mutC mutator alleles to the glyV and glyW glycine tRNA genes, respectively, and the subsequent discovery that the mutA phenotype is abolished in a DeltarecA strain raise the possibility that asp --> gly misinsertion may induce a novel mutagenic pathway. The recA requirement suggests three possibilities: (i) the SOS mutagenesis pathway is activated in mutA cells; (ii) loss of recA function interferes with mutA-promoted asp --> gly misinsertion; or (iii) a hitherto unrecognized recA-dependent mutagenic pathway is activated by translational stress. By assaying the expression levels of a reporter plasmid bearing a umuC :lacZ fusion, we show that the SOS regulon is not in a derepressed state in mutA cells. Neither overexpression of the lexA gene through a multicopy plasmid nor replacement of the wild-type lexA allele with the lexA1[Ind-] allele interferes with the expression of the mutA phenotype. The mutA phenotype is unaffected in cells defective for dinB, as shown here, and is unaffected in cells defective for umuD and umuC genes, as shown previously. We show that mutA-promoted asp --> gly misinsertion occurs in recA- cells and, therefore, the requirement for recA is 'downstream' of mistranslation. Finally, we show that the mutA phenotype is abolished in cells deficient for recB, suggesting that cellular recombination functions may be required for the expression of the mutator phenotype. We propose that translational stress induces a previously unrecognized mutagenic pathway in Escherichia coli.

Alternate JournalMol. Microbiol.
PubMed ID10320582
Grant ListCA73026 / CA / NCI NIH HHS / United States
GM58253 / GM / NIGMS NIH HHS / United States