title: Amber dnaG mutation exerting a polar effect on the synthesis of RNA polymerase sigma factor in Escherichia coli.
abstract: Three amber mutants of Escherichia coli, dnaG9, dnaG24 and dnaG26, affected in the structural gene (dnaG) for "primase" have been isolated from a parental strain carrying a temperature-sensitive amber suppressor (supF-Ts6). These mutants grow at 30 degrees C but not at 42 degrees C since primase is essential for growth and is synthesized only at low temperatures. Chimeric plasmids carrying dnaG+ but no other chromosomal genes of E. coli complemented the amber mutations, and the plasmid carrying a part of dnaG lost the complementing activity. Beside, plasmids carrying a dnaG amber mutation complemented a temperature-sensitive dnaG mutation only in the presence of amber suppressor. One of the amber mutations, dnaG24 which maps proximal to the NH2-terminus of the dnaG gene, exerted a polar effect on the synthesis of RNA polymerase sigma factor in E. coli.
mesh_terms: D019915:DNA Primase; D004926:Escherichia coli / Q000235:genetics*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D009154:Mutation; D012316:RNA Nucleotidyltransferases / Q000235:genetics*; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D012808:Sigma Factor; D014157:Transcription Factors; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases