Genetic Dissection of an Inhibitor of the Sporulation Sigma Factor σG

A Small Protein Required for the Switch from σ F to σ G during Sporulation in Bacillus subtilis

“…Thus, fin represents a previously unrecognized and uncharacterized sporulation gene. Given the similarity of Fin to the anti-G factor CsfB (also called Gin) (7,11,19,29), as presented herein, we speculate that Fin functions as an anti-F factor which, by antag-onizing F , facilitates the switch to G and promotes the transition to late developmental gene expression in the forespore.…”

“…Accession numbers for protein sequences are listed in Materials and Methods. Note that CsfB is also conserved more widely in endospore formers, including Clostridium species, and that multiple sequence alignments of the entire CsfB family have been published previously (19,29 (13). Indeed, the csfB promoter (P csfB ), like P spoIIQ , was more active in fin cells (data not shown).…”

“…3). As drawn to our attention by A. Henriques and P. Stragier (personal communications), this makes Fin similar to the anti-G factor CsfB (also known as Gin) (7,11,19,29). CsfB is also a small, highly conserved protein harboring two invariant Cys-X-X-Cys motifs (Fig.…”

“…One possible clue comes from the similarity of Fin to the anti-G factor CsfB. CsfB is a potent inhibitor of G and is likely to accomplish this by binding to the sigma factor (19,29), although a direct biochemical interaction between CsfB and G has not yet been demonstrated. CsfB was proposed to be the key target of an intercellular signaling pathway controlling G activity in the forespore (19), but other work has convincingly indicated that the anti-G factor instead plays an auxiliary role in preventing premature G activation (see above) (7,11).…”

Inactivation of σ F in Clostridium acetobutylicum ATCC 824 Blocks Sporulation Prior to Asymmetric Division and Abolishes σ E and σ G Protein Expression but Does Not Block Solvent Formation

“…These six are well-characterized genes of the F regulon of B. subtilis (56) for which strong homologs can be identified on the C. acetobutylicum genome, and of the six, csfB and gpr-spoIIP (which are pre- dicted to be transcribed as an operon [39]) have a predicted F/G -binding motif, a binding motif for either F or G (39). In B. subtilis, CsfB (also called Gin) is believed to bind G to prevent premature transcriptional activity (6,21,42); gpr encodes a protease responsible for the degradation of small acidsoluble proteins (SASPs) during germination (44,49); SpoIIP is involved in the dissolution of the septal cell wall and is required for engulfment (16); lonB encodes an ATP-dependent protease whose precise function is unknown (46); SpoIIR is necessary for triggering the processing of pro-E into E (22,29); and sigG encodes G . The expression of these six genes was examined in both the WT and FKO1 at 12, 24, and 36 h, and expression ratios were calculated (Table 1).…”