We have been studying the role that protein degradation plays in regulating gene expression and have initiated a study on the linkages between chromosome synthesis and partition of chromosomes during cell division. We have continued our study of the mechanism of regulation of capsule synthesis, as a model for understanding the role of unstable proteins as regulators. RcsA, a target for the Lon protease, was shown to interact with another regulator, RcsB, in a temperature sensitive manner. Studies on rcsA expression have demonstrated a trans-acting role for a site downstream of the structural gene in regulating rcsA. We have continued studies on a new proteolytic activity capable of degading the Lon substrates, RcsA and SulA, which appears when a multicopy plasmid carrying a gene we have called alp is introduced into cells. The new activity is dependent on excision of a cryptic prophage and consequent inactivation of a chromosomal gene encoding a stable RNA. A third energy-dependent protease under study is the two component Clp protease. We are continuing mutagenesis studies of the CIpP subunit to determine the specificity and role of CIpP-dependent CIpP processing for assembly and proteolytic activity. In a separate project, camphor resistant mutations in four different loci have been shown by flow cytometry to lead to increased ploidy. In combination with previous genetic analysis, this suggests these mutations (called mbr) define three different coupling events for chromosome number and cell cycle.
