title: Engulfment-regulated proteolysis of SpoIIQ: evidence that dual checkpoints control sigma activity.
abstract: During Bacillus subtilis sporulation, the engulfment checkpoint is thought to directly regulate late forespore transcription but to indirectly regulate late mother cell transcription, via the sigmaG-produced protease SpoIVB. We here demonstrate that SpoIIQ is subject to sigmaG-independent, but engulfment-dependent, proteolysis that depends on SpoIVB. Thus, SpoIVB produced before engulfment supports some SpoIVB-dependent events, suggesting that its activity or access to substrates must be regulated by engulfment. Furthermore, a mutation (bofA) that allows sigmaK to be active without sigmaG does not allow sigmaK activity in engulfment mutants, although the pro-sigmaK processing enzyme (SpoIVFB) is localized to the septum in engulfment mutants, suggesting that engulfment comprises a second checkpoint for sigmaK Finally, we find that SpoIIQ and another protein required for sigmaG activity (SpoIIIAH), which directly interact and assemble helical structures around the forespore, recruit the sigmaK-processing enzyme SpoIVFB to the forespore and these structures. We suggest that these foci serve a synapse-like role, allowing engulfment to simultaneously control both sigmaG and sigmaK, and integrating multiple checkpoints and signalling pathways.
authors.affiliation: Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Jiang
authors.forename: Aileen
authors.initials: A
authors.lastname: Rubio
authors.forename: Shinobu
authors.initials: S
authors.lastname: Chiba
authors.forename: Kit
authors.initials: K
authors.lastname: Pogliano
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010450:Endopeptidases / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D012097:Repressor Proteins / Q000502:physiology; D012808:Sigma Factor / Q000378:metabolism; D013171:Spores, Bacterial / Q000737:chemistry; D014157:Transcription Factors / Q000502:physiology*; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C112176:pro-sigmaK protein, Bacillus subtilis; C084190:sigma K; C030069:spore-specific proteins, Bacillus; C074423:bofA protein, Bacillus subtilis; C071441:spoIVFA protein, Bacillus subtilis; D049452:Green Fluorescent Proteins; D001616:beta-Galactosidase; D010450:Endopeptidases; C071442:spoIVFB protein, Bacillus subtilis