Protective role for H-NS protein in IS1 transposition.
The transposase (InsAB') of the insertion element IS1 can create breaks in DNA that lead to induction of the SOS response. We have used the SOS response to InsAB' to screen for host mutations that affect InsAB' function and thus point to host functions that contribute to the IS1 transposition mechanism. Mutations in the hns gene, which codes for a DNA binding protein with wide-ranging effects on gene expression, abolish the InsAB'-induced SOS response. They also reduce transposition, whether by simple insertion or cointegrate formation, at least 100-fold compared with the frequency seen in hns+ cells. Examination of protein profiles revealed that in an hns-null mutant, InsAB' is undetectable under conditions where it constitutes the most abundant protein in hns+ cells. Likewise, brief labeling of the hns cells with [35S]methionine revealed very small amounts of InsAB', and this was undetectable after a short chase. Transcription from the promoters used to express insAB' was essentially unaltered in hns cells, as was the level of insAB' mRNA. A mutation in lon, but not in ftsH or clpP, restored InsAB' synthesis in the hns strain, and a mutation in ssrA partially restored it, implying that the absence of H-NS leads to a problem in completing translation of insAB' mRNA and/or degradation of nascent InsAB' protein.
Rouquette
Claudine
C
Laboratoire de Microbiologie et Génétique Moléculaire, CNRS, Toulouse, France.
Serre
Marie-Claude
MC
Lane
David
D
D049069:ATP-Dependent Proteases; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D049070:Protease La; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013014:SOS Response, Genetics; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D006360:Heat-Shock Proteins; C088046:InsB protein, E coli; D011506:Proteins; D012097:Repressor Proteins; C064548:insA1 protein, E coli; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; C483567:Lon protein, E coli; D049070:Protease La