The characterization of terminators of RNA transcription on IS30 and an analysis of their role in IS element-mediated polarity.
Using expression vectors carrying the lacUV5 or Pgal promoters and the galK gene, we have studied terminators of transcription on the prokaryotic mobile genetic element IS30. The long open reading frame, ORF-A, of IS30 contains a relatively Rho-independent terminator, T30A, within its coding sequence. T30A terminates the majority of transcripts initiated at either an external promoter or the IS30-borne promoter P30A. No other terminator functions on this strand of IS30 (orientation left to right). In the orientation right to left, the previously identified terminator T30C, which follows ORF-C, is Rho-independent. T30C together with T30D, a newly identified, strong, partially Rho-dependent terminator near the left end of IS30, permits less than 2% read-through from external promoters. Neither ORF-A nor ORF-C appears to be protected from transcription by external promoters. As a consequence of the internal terminators, the insertion of IS30 into an operon can be expected to reduce the expression of genes downstream of the site of insertion weakly for one orientation of IS30 and strongly for the other orientation.
D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics; D005686:Galactokinase / Q000235:genetics; D005796:Genes; D005798:Genes, Bacterial; D005809:Genes, Regulator; D005822:Genetic Vectors; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics*; D012234:Rho Factor / Q000378:metabolism; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
D004251:DNA Transposable Elements; D012329:RNA, Bacterial; D012234:Rho Factor; D005686:Galactokinase; D004262:DNA Restriction Enzymes