title: Mechanism of expression of DNA repair gene vsr, an Escherichia coli gene that overlaps the DNA cytosine methylase gene, dcm.
abstract: The DNA cytosine methylase gene of Escherichia coli, dcm, overlaps an open reading frame (ORF) that continues in +1 register past the end of dcm. This ORF codes for a gene, vsr, that is required for a T:G to C:G base mismatch correction process. In this study, mutants that affect the level of expression of the two genes were constructed and characterized. Further, a previously isolated mutant, dcm-6, was cloned and mutations within it were identified. Northern blots were used to identify dcm-specific RNA species in wild type and dcm-6 cells. Based on these studies we conclude that there is a six-codon overlap between vsr and dcm. The two proteins appear to be made from a single RNA transcript and translation of dcm is required for the efficient synthesis of Vsr. Further, Vsr is active by itself and may not be produced as a fusion with Dcm. This is the first example of chromosomal genes that overlap in their coding regions and produce proteins with distinct functions.
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan 48202.
authors.forename: M E
authors.initials: ME
authors.lastname: Dar
authors.forename: A S
authors.initials: AS
authors.lastname: Bhagwat
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D004260:DNA Repair / Q000235:genetics*; D004269:DNA, Bacterial / Q000378:metabolism*; D015257:DNA-Cytosine Methylases / Q000235:genetics*; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005807:Genes, Overlapping; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D015257:DNA-Cytosine Methylases