ClpAP is an auxiliary protease for DnaA degradation in Caulobacter crescentus.
The Clp family of proteases is responsible for controlling both stress responses and normal growth. In Caulobacter crescentus, the ClpXP protease is essential and drives cell cycle progression through adaptor-mediated degradation. By contrast, the physiological role for the ClpAP protease is less well understood with only minor growth defects previously reported for ΔclpA cells. Here, we show that ClpAP plays an important role in controlling chromosome content and cell fitness during extended growth. Cells lacking ClpA accumulate aberrant numbers of chromosomes upon prolonged growth suggesting a defect in replication control. Levels of the replication initiator DnaA are elevated in ΔclpA cells and degradation of DnaA is more rapid in cells lacking the ClpA inhibitor ClpS. Consistent with this observation, ClpAP degrades DnaA in vitro while ClpS inhibits this degradation. In cells lacking Lon, the protease previously shown to degrade DnaA in Caulobacter, ClpA overexpression rescues defects in fitness and restores degradation of DnaA. Finally, we show that cells lacking ClpA are particularly sensitive to inappropriate increases in DnaA activity. Our work demonstrates an unexpected effect of ClpAP in directly regulating replication through degradation of DnaA and expands the functional role of ClpAP in Caulobacter.
Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA.
Jing
J
Liu
Department of Biology, University of Massachusetts Amherst, Amherst, MA, USA.
Laura I
LI
Francis
Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
Kristina
K
Jonas
Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
Michael T
MT
Laub
Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA.
Peter
P
Chien
D001426:Bacterial Proteins / Q000378:metabolism; D016934:Caulobacter / Q000235:genetics; D016935:Caulobacter crescentus / Q000235:genetics* / Q000378:metabolism*; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D049071:Endopeptidase Clp / Q000378:metabolism*; D010447:Peptide Hydrolases
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D010447:Peptide Hydrolases; D049071:Endopeptidase Clp
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