AUTHOR=Fujita Yasutaro , Ogura Mitsuo , Nii Satomi , Hirooka Kazutake 

TITLE=Dual Regulation of Bacillus subtilis kinB Gene Encoding a Sporulation Trigger by SinR through Transcription Repression and Positive Stringent Transcription Control

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02502

DOI=10.3389/fmicb.2017.02502

ISSN=1664-302X

ABSTRACT=<p>It is known that transcription of <italic>kinB</italic> encoding a trigger for <italic>Bacillus subtilis</italic> sporulation is under repression by SinR, a master repressor of biofilm formation, and under positive stringent transcription control depending on the adenine species at the transcription initiation nucleotide (nt). Deletion and base substitution analyses of the <italic>kinB</italic> promoter (P<italic><sub>kinB</sub></italic>) region using <italic>lacZ</italic> fusions indicated that either a 5-nt deletion (Δ5, nt -61/-57, +1 is the transcription initiation nt) or the substitution of G at nt -45 with A (G-45A) relieved <italic>kinB</italic> repression. Thus, we found a pair of SinR-binding consensus sequences (GTTCTYT; Y is T or C) in an inverted orientation (SinR-1) between nt -57/-42, which is most likely a SinR-binding site for <italic>kinB</italic> repression. This relief from SinR repression likely requires SinI, an antagonist of SinR. Surprisingly, we found that SinR is essential for positive stringent transcription control of P<italic><sub>kinB</sub></italic>. Electrophoretic mobility shift assay (EMSA) analysis indicated that SinR bound not only to SinR-1 but also to SinR-2 (nt -29/-8) consisting of another pair of SinR consensus sequences in a tandem repeat arrangement; the two sequences partially overlap the ‘-35’ and ‘-10’ regions of P<italic><sub>kinB</sub></italic>. Introduction of base substitutions (T-27C C-26T) in the upstream consensus sequence of SinR-2 affected positive stringent transcription control of P<italic><sub>kinB</sub></italic>, suggesting that SinR binding to SinR-2 likely causes this positive control. EMSA also implied that RNA polymerase and SinR are possibly bound together to SinR-2 to form a transcription initiation complex for <italic>kinB</italic> transcription. Thus, it was suggested in this work that derepression of <italic>kinB</italic> from SinR repression by SinI induced by Spo0A∼P and occurrence of SinR-dependent positive stringent transcription control of <italic>kinB</italic> might induce effective sporulation cooperatively, implying an intimate interplay by stringent response, sporulation, and biofilm formation.</p>