Control of transcription of the Bacillus subtilis spoIIIG gene, which codes for the forespore-specific transcription factor sigma G.
The Bacillus subtilis spoIIIG gene codes for a sigma factor termed sigma G which directs transcription of genes expressed only in the forespore compartment of the sporulating cell. Use of spoIIIG-lacZ transcriptional fusions showed that spoIIIG is cotranscribed with the spoIIG operon beginning at t0.5-1 of sporulation. However, this large mRNA produced little if any sigma G, and transferring the spoIIIG gene without the spoIIG promoter into the amyE locus resulted in a Spo+ phenotype. Significant translation of spoIIIG began at t2.5-3 with use of an mRNA whose 5' end is just upstream of the spoIIIG coding sequence. Synthesis of this spoIIIG-specific mRNA was not abolished by a deletion in spoIIIG itself. Similar results were obtained when a spoIIIG-lacZ translational fusion lacking the spoIIG promoter was integrated at the amyE locus. These data suggest that synthesis of sigma G is dependent neither on transcription from the spoIIG promoter nor on sigma G itself but can be due to another transcription factor. This transcription factor may be sigma F, the product of the spoIIAC locus, since a spoIIAC mutation blocked spoIIIG expression, and sequences upstream of the 5' end of the spoIIIG-specific mRNA agree well with the recognition sequence for sigma F. RNA polymerase containing sigma F (E sigma F) initiated transcription in vitro on a spoIIIG template at the 5' end found in vivo, as did E sigma G. However, E sigma F showed a greater than 20-fold preference for spoIIIG over a known sigma G-dependent gene compared with the activity of E sigma G.
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Department of Biochemistry, University of Connecticut Health Center, Farmington 06032.
Cabrera-Martinez
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Setlow
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D001412:Bacillus subtilis / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis*; D013170:Spores; D014157:Transcription Factors / Q000096:biosynthesis*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
D012333:RNA, Messenger; D014157:Transcription Factors; D001616:beta-Galactosidase