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Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

Serrano M, Gao J, Bota J, Bate AR, Meisner J, Eichenberger P, Moran CP, Henriques AO - PLoS Genet. (2015)

Bottom Line: We also show that CsfB prevents activation of σG in the mother cell and the premature σG-dependent activation of σK.The capacity of CsfB to directly block σE activity may also explain how CsfB plays a role as one of the several mechanisms that prevent σE activation in the forespore.Thus the capacity of CsfB to differentiate between the highly similar σF/σG and σE/σK pairs allows it to rinforce the cell-type specificity of these sigma factors and the transition from early to late development in B. subtilis, and possibly in all sporeformers that encode a CsfB orthologue.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Estação Agronómica Nacional, Oeiras, Portugal.

ABSTRACT
Gene expression during spore development in Bacillus subtilis is controlled by cell type-specific RNA polymerase sigma factors. σFand σE control early stages of development in the forespore and the mother cell, respectively. When, at an intermediate stage in development, the mother cell engulfs the forespore, σF is replaced by σG and σE is replaced by σK. The anti-sigma factor CsfB is produced under the control of σF and binds to and inhibits the auto-regulatory σG, but not σF. A position in region 2.1, occupied by an asparagine in σG and by a glutamate in οF, is sufficient for CsfB discrimination of the two sigmas, and allows it to delay the early to late switch in forespore gene expression. We now show that following engulfment completion, csfB is switched on in the mother cell under the control of σK and that CsfB binds to and inhibits σE but not σK, possibly to facilitate the switch from early to late gene expression. We show that a position in region 2.3 occupied by a conserved asparagine in σE and by a conserved glutamate in σK suffices for discrimination by CsfB. We also show that CsfB prevents activation of σG in the mother cell and the premature σG-dependent activation of σK. Thus, CsfB establishes negative feedback loops that curtail the activity of σE and prevent the ectopic activation of σG in the mother cell. The capacity of CsfB to directly block σE activity may also explain how CsfB plays a role as one of the several mechanisms that prevent σE activation in the forespore. Thus the capacity of CsfB to differentiate between the highly similar σF/σG and σE/σK pairs allows it to rinforce the cell-type specificity of these sigma factors and the transition from early to late development in B. subtilis, and possibly in all sporeformers that encode a CsfB orthologue.

No MeSH data available.


Related in: MedlinePlus

Model for the functions of CsfB.A: following engulfment completion, two negative feedback loops are established that act to limit the level (brown line) and the activity of σE (red line). The loop that acts at the level of σE activity involves the σK-dependent production of CsfB (this work), and restricts mainly the expression of the σE-and SpoIIID-dependent gene class. Both feedback loops promote proper switching from the early (pre-engulfment, σE-dependent) to late (post-engulfment completion, σK-dependent) stages in development. Together with LonA and SpoIIAB, CsfB also antagonizes σG in the mother cell (grey line). Minimizing the chances of σG becoming active in the mother cell prevents the premature, forespore-independent activation of σK. Thus, the action of CsfB superimposes both onto the transcriptional and cell-cell signaling networks. B: the panel represents the residues that allow binding of CsfB to σG (N45) and σE (N100), and that are sufficient to render σF (E39) and σK (E93) resistant to the anti-sigma factor. N45 in σG and E39 in σF are located in conserved region 2.1 (purple sector) whereas N100 in σE and E93 in σE are located in region 2.3 (yellow).
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pgen.1005104.g008: Model for the functions of CsfB.A: following engulfment completion, two negative feedback loops are established that act to limit the level (brown line) and the activity of σE (red line). The loop that acts at the level of σE activity involves the σK-dependent production of CsfB (this work), and restricts mainly the expression of the σE-and SpoIIID-dependent gene class. Both feedback loops promote proper switching from the early (pre-engulfment, σE-dependent) to late (post-engulfment completion, σK-dependent) stages in development. Together with LonA and SpoIIAB, CsfB also antagonizes σG in the mother cell (grey line). Minimizing the chances of σG becoming active in the mother cell prevents the premature, forespore-independent activation of σK. Thus, the action of CsfB superimposes both onto the transcriptional and cell-cell signaling networks. B: the panel represents the residues that allow binding of CsfB to σG (N45) and σE (N100), and that are sufficient to render σF (E39) and σK (E93) resistant to the anti-sigma factor. N45 in σG and E39 in σF are located in conserved region 2.1 (purple sector) whereas N100 in σE and E93 in σE are located in region 2.3 (yellow).

Mentions: Genome-wide transcriptional profiling analysis showed that inactivation of PsigK, which abolishes CsfB accumulation in the mother cell, caused increased transcription of σE-controlled genes that either rely solely on σE for expression or are dependent on the type I coherent FFL formed by σE and the ancillary transcriptional activator SpoIIID [9]. Increased σE activity was also observed using a σE-responsive lacZ reporter in a strain expressing the CsfB-resistant form of σE (σE N100E). By contrast, σE-dependent genes repressed by GerR or SpoIIID (i.e., the output of the type I incoherent FFLs generating pulses X2 and X3 in Fig. 1B) did not show increased expression in the PsigF-csfB strain, most likely because their transcription has already been switched off at the time of analysis due to the action of the two repressors (Fig. 3A). In general, these observations are consistent with an increase in the activity of σE in the absence of CsfB and with the properties of the FFLs formed by σE [3]. They also support a model in which the appearance of CsfB in the mother cell promotes the transition from early to late cell-type specific gene expression (i.e., the σE to σK switch) (Fig. 8A).


Dual-specificity anti-sigma factor reinforces control of cell-type specific gene expression in Bacillus subtilis.

Serrano M, Gao J, Bota J, Bate AR, Meisner J, Eichenberger P, Moran CP, Henriques AO - PLoS Genet. (2015)

Model for the functions of CsfB.A: following engulfment completion, two negative feedback loops are established that act to limit the level (brown line) and the activity of σE (red line). The loop that acts at the level of σE activity involves the σK-dependent production of CsfB (this work), and restricts mainly the expression of the σE-and SpoIIID-dependent gene class. Both feedback loops promote proper switching from the early (pre-engulfment, σE-dependent) to late (post-engulfment completion, σK-dependent) stages in development. Together with LonA and SpoIIAB, CsfB also antagonizes σG in the mother cell (grey line). Minimizing the chances of σG becoming active in the mother cell prevents the premature, forespore-independent activation of σK. Thus, the action of CsfB superimposes both onto the transcriptional and cell-cell signaling networks. B: the panel represents the residues that allow binding of CsfB to σG (N45) and σE (N100), and that are sufficient to render σF (E39) and σK (E93) resistant to the anti-sigma factor. N45 in σG and E39 in σF are located in conserved region 2.1 (purple sector) whereas N100 in σE and E93 in σE are located in region 2.3 (yellow).
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Related In: Results  -  Collection

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pgen.1005104.g008: Model for the functions of CsfB.A: following engulfment completion, two negative feedback loops are established that act to limit the level (brown line) and the activity of σE (red line). The loop that acts at the level of σE activity involves the σK-dependent production of CsfB (this work), and restricts mainly the expression of the σE-and SpoIIID-dependent gene class. Both feedback loops promote proper switching from the early (pre-engulfment, σE-dependent) to late (post-engulfment completion, σK-dependent) stages in development. Together with LonA and SpoIIAB, CsfB also antagonizes σG in the mother cell (grey line). Minimizing the chances of σG becoming active in the mother cell prevents the premature, forespore-independent activation of σK. Thus, the action of CsfB superimposes both onto the transcriptional and cell-cell signaling networks. B: the panel represents the residues that allow binding of CsfB to σG (N45) and σE (N100), and that are sufficient to render σF (E39) and σK (E93) resistant to the anti-sigma factor. N45 in σG and E39 in σF are located in conserved region 2.1 (purple sector) whereas N100 in σE and E93 in σE are located in region 2.3 (yellow).
Mentions: Genome-wide transcriptional profiling analysis showed that inactivation of PsigK, which abolishes CsfB accumulation in the mother cell, caused increased transcription of σE-controlled genes that either rely solely on σE for expression or are dependent on the type I coherent FFL formed by σE and the ancillary transcriptional activator SpoIIID [9]. Increased σE activity was also observed using a σE-responsive lacZ reporter in a strain expressing the CsfB-resistant form of σE (σE N100E). By contrast, σE-dependent genes repressed by GerR or SpoIIID (i.e., the output of the type I incoherent FFLs generating pulses X2 and X3 in Fig. 1B) did not show increased expression in the PsigF-csfB strain, most likely because their transcription has already been switched off at the time of analysis due to the action of the two repressors (Fig. 3A). In general, these observations are consistent with an increase in the activity of σE in the absence of CsfB and with the properties of the FFLs formed by σE [3]. They also support a model in which the appearance of CsfB in the mother cell promotes the transition from early to late cell-type specific gene expression (i.e., the σE to σK switch) (Fig. 8A).

Bottom Line: We also show that CsfB prevents activation of σG in the mother cell and the premature σG-dependent activation of σK.The capacity of CsfB to directly block σE activity may also explain how CsfB plays a role as one of the several mechanisms that prevent σE activation in the forespore.Thus the capacity of CsfB to differentiate between the highly similar σF/σG and σE/σK pairs allows it to rinforce the cell-type specificity of these sigma factors and the transition from early to late development in B. subtilis, and possibly in all sporeformers that encode a CsfB orthologue.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Estação Agronómica Nacional, Oeiras, Portugal.

ABSTRACT
Gene expression during spore development in Bacillus subtilis is controlled by cell type-specific RNA polymerase sigma factors. σFand σE control early stages of development in the forespore and the mother cell, respectively. When, at an intermediate stage in development, the mother cell engulfs the forespore, σF is replaced by σG and σE is replaced by σK. The anti-sigma factor CsfB is produced under the control of σF and binds to and inhibits the auto-regulatory σG, but not σF. A position in region 2.1, occupied by an asparagine in σG and by a glutamate in οF, is sufficient for CsfB discrimination of the two sigmas, and allows it to delay the early to late switch in forespore gene expression. We now show that following engulfment completion, csfB is switched on in the mother cell under the control of σK and that CsfB binds to and inhibits σE but not σK, possibly to facilitate the switch from early to late gene expression. We show that a position in region 2.3 occupied by a conserved asparagine in σE and by a conserved glutamate in σK suffices for discrimination by CsfB. We also show that CsfB prevents activation of σG in the mother cell and the premature σG-dependent activation of σK. Thus, CsfB establishes negative feedback loops that curtail the activity of σE and prevent the ectopic activation of σG in the mother cell. The capacity of CsfB to directly block σE activity may also explain how CsfB plays a role as one of the several mechanisms that prevent σE activation in the forespore. Thus the capacity of CsfB to differentiate between the highly similar σF/σG and σE/σK pairs allows it to rinforce the cell-type specificity of these sigma factors and the transition from early to late development in B. subtilis, and possibly in all sporeformers that encode a CsfB orthologue.

No MeSH data available.


Related in: MedlinePlus