Nucleic Acids Research, 1988, Vol. 16, No. 23 11285-11301
© 1988
MOLECULAR BIOLOGY |
Autoregulation of phage µ transposase at the level of translation
Research Institute of Scripps Clinic, Department of Molecular Biology La Jolla, CA 92037, USA
Received April 18, 1988. Revised October 26, 1988. Accepted October 26, 1988.
The bacteriophage Mu A and B genes, which lie adjacent to each other and are colinear on the phage genome, encode proteins that catalyze efficient transposition of Mu DNA. We show that the molar ratio of A and B proteins is approximately 1:20 in extracts prepared after induction of cells containing a Mu lysogen or a plasmid carrying the Mu fragment that encompasses A and B. In cells harboring the cloned genes, the proteins are synthesized from a single transcript. Pulse-chase experiments demonstrate that the lower amounts of A protein are not from preferential turnover of this protein. This suggests the existence of a post-transcriptional mechanism to down-regulate A protein synthesis. From an analysis of the activity of several ß-galactosidase fusions to A protein, we infer that A protein may repress its own translation. By an agarose gel mobility-shift assay, we demonstrate that purified A protein binds specifically in vitro to its mRNA.