Nucleic Acids Research, 1994, Vol. 22, No. 10 1855-1860
© 1994
MOLECULAR BIOLOGY |
The ß recombinase from the Streptococcal plasmid pSM19035 represses its own transcription by holding the RNA polymerase at the promoter region
1Centro Nacional de Biotecnología, C.S.I.C., Campus Universidad Autónoma 28049 Madrid 2Centro de Biología Molecular ‘Severo Ochoa’, C.S.I.C., Universidad Autónoma Canto Blanco, 28049 Madrid, Spain 3Max-Planck-Institut für molekulare Genetik Ihnestrasse 73, D-14195 Berlin, Germany
*To whom correspondence should be addressed at: Centro Nacional de Biotecnología, C.S.I.C., Campus Universidad Autónoma, 28049 Madrid, Spain.
Received February 2, 1994. Revised April 12, 1994. Accepted April 12, 1994.
The ß protein encoded by the Streptococcus pyogenes plasmid pSM19035 is a site-specific recombinase involved in both resolution of plasmid multimers into monomers and DNA inversion. It has been proposed that the DNA region to which the ß recombinase binds to mediate recombination includes a promoter from which orf
and the ß gene are transcribed. We have determined the sites at which transcription of the orf and the ß gene initiates in vitro and we have demonstrated that highly purified ß recombinase acts as a repressor of its own synthesis. The promoters are located within the ß recombinase binding site, which we have defined previously. The binding of the ß recombinase to its target site does not seem to exclude RNA polymerase from the promoter, despite the overlapping of their binding sites. Therefore, it is likely that the ß recombinase does not repress transcription by a mere steric hindrance on RNA polymerase binding.