Multilevel regulation of the sporulation transcription factor sigma K in Bacillus subtilis.
Gene expression in the mother-cell compartment of the Bacillus subtilis sporangium is governed in part by the sporulation transcription factor sigma K. The production of sigma K is controlled at three levels: by a chromosomal rearrangement that generates the sigma K-coding sequence (sigK), by compartment-specific transcription of sigK, and by conversion of the inactive pro-protein product of sigK (pro-sigma K) to sigma K. To investigate the function of these multiple levels of regulation, we constructed a set of strains that bypass the chromosomal rearrangement, pro-protein processing, or both levels of control. Here we show that one of the functions of the chromosomal rearrangement and pro-protein processing is to prevent inappropriate production of sigma K under nonsporulation conditions. In the absence of both of these levels of control, a low level of sigma K-directed gene expression is observed during stationary phase after growth in rich medium. The appearance of sigma K under these conditions is probably due to a low level of sigma K-directed transcription from the sigK promoter in a positive feedback loop. We also report the construction of a strain that produces high levels of sigma K during growth. Using this strain, we demonstrate that the production of sigma K during growth is sufficient to induce a cascade of gene expression that closely mimics late events in the mother-cell line of gene expression.
Oke
V
V
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Losick
R
R
D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D003001:Cloning, Molecular; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007700:Kinetics; D016296:Mutagenesis; D013171:Spores, Bacterial / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000378:metabolism
D014157:Transcription Factors; C084190:sigma K; D001616:beta-Galactosidase