An essential transcription factor, SciP, enhances robustness of Caulobacter cell cycle regulation.
A cyclical control circuit composed of four master regulators drives the Caulobacter cell cycle. We report that SciP, a helix-turn-helix transcription factor, is an essential component of this circuit. SciP is cell cycle-controlled and co-conserved with the global cell cycle regulator CtrA in the α-proteobacteria. SciP is expressed late in the cell cycle and accumulates preferentially in the daughter swarmer cell. At least 58 genes, including many flagellar and chemotaxis genes, are regulated by a type 1 incoherent feedforward motif in which CtrA activates sciP, followed by SciP repression of ctrA and CtrA target genes. We demonstrate that SciP binds to DNA at a motif distinct from the CtrA binding motif that is present in the promoters of genes co-regulated by SciP and CtrA. SciP overexpression disrupts the balance between activation and repression of the CtrA-SciP coregulated genes yielding filamentous cells and loss of viability. The type 1 incoherent feedforward circuit motif enhances the pulse-like expression of the downstream genes, and the negative feedback to ctrA expression reduces peak CtrA accumulation. The presence of SciP in the control network enhances the robustness of the cell cycle to varying growth rates.
Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Meng How
MH
Tan
Jennifer B
JB
Kozdon
Xiling
X
Shen
Lucy
L
Shapiro
Harley H
HH
McAdams
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016934:Caulobacter / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D019077:Helix-Turn-Helix Motifs; D011485:Protein Binding / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; C097706:CtrA protein, Caulobacter; D004268:DNA-Binding Proteins; D014157:Transcription Factors