Factors affecting transposition activity of IS50 and Tn5 ends.
The partially matched I and O ends of IS50 (the insertion sequence of the transposon Tn5) are needed for transposition, probably as the sites upon which the cis-acting transposase and host proteins act. To better understand how transposition is regulated we made a series of IS50-related elements in which the positions of the ends and of the transposase gene were varied systematically. Assays of these elements showed that the I and O ends differ inherently in transposition activity. Other workers showed that methylation, at DNA N6-adenine methyltransferase (Dam) recognition sites within the I end and the transposase tnp gene promoter, inhibits transposase synthesis and also I end activity. We show that the effect of Dammediated methylation on an I end depends on the end's orientation relative to the tnp gene. Further, in dam+ cells oriented like -tnp----in relation to the first and second ends) are (O, I) greater than (O, O) greater than or equal to (I, O) greater than (I, I). In dam- cells the relative activities are (O, I) = (I, O) = (I, I) greater than (O, O). Our results are consistent with a model orginally developed for IS10, in which hemi-methylation resulting from passage of a replication fork regulates transposition.
Dodson
K W
KW
Department of Microbiology and Immunology, Washington University Medical School, St. Louis, MO 63110.
Berg
D E
DE
D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D004251:DNA Transposable Elements; D004274:DNA, Recombinant; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics; D010957:Plasmids; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D014158:Transcription, Genetic; D014161:Transduction, Genetic; D019895:Transposases
D004251:DNA Transposable Elements; D004274:DNA, Recombinant; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D009713:Nucleotidyltransferases; D019895:Transposases