Spatio-temporal control of DNA replication by the pneumococcal cell cycle regulator CcrZ

Abstract

Most bacteria replicate and segregate their DNA concomitantly while growing, before cell division takes place. How bacteria synchronize these different cell cycle events to ensure faithful chromosome inheritance is poorly understood.Here, we identified a conserved and essential protein in pneumococci and related Firmicutes named CcrZ (for Cell Cycle Regulator protein interacting with FtsZ) that couples cell division with DNA replication by controlling the activity of the master initiator of DNA replication, DnaA. The absence of CcrZ causes mis-timed and reduced initiation of DNA replication, which subsequently results in aberrant cell division. We show that CcrZ from Streptococcus pneumoniae directly interacts with the cytoskeleton protein FtsZ to place it in the middle of the newborn cell where the DnaA-bound origin is positioned. Together, this work uncovers a new mechanism for the control of the bacterial cell cycle in which CcrZ controls DnaA activity to ensure that the chromosome is replicated at the right time during the cell cycle.to alter cell size in E. coli and B. subtilis but the converse was not true for B. subtilis 24,25 . Taken together, current data indicates that bacteria evolved different mechanisms to coordinate their cell cycle events.Although E. coli and B. subtilis use different systems for regulating their cell cycle, the way they localize their division site is conserved, as both organisms use a variant of the Min system to prevent polymerization of the tubulin-like protein

Multiple mechanisms for overcoming lethal over-initiation of DNA replication

“…The effects of ccrZ in S. pneumoniae and B. subtilis are described in other work (Gallay et al, 2019).…”

“…ytmP (ccrZ). We isolated several mutations in a previously uncharacterized gene, ytmP, now called ccrZ (Gallay et al, 2019). The ccrZ gene product has regions of similarity to choline and enthanolamine kinases (Zimmermann et al, 2018).…”

The RecA-directed recombination pathway of natural transformation initiates at chromosomal replication forks in Streptococcus pneumoniae

“…Second, this tDNA was co-purified with YFP-DnaX at a similar level to DprA-GFP (Figure 4E), suggesting close proximity between early DprA-mediated HR intermediates and chromosomal replication forks during transformation. We also used a NanoBit assay 49, 50 to explore the proximity of DprA engaged in transformation with the replisome. This system employs a luciferase separated into a large bit (LgBit) and a small bit (SmBit).…”

SmdA is a novel cell morphology determinant in Staphylococcus aureus

“…Cell division in S. aureus occurs in alternating orthogonal planes, meaning that the new cell division plane is always perpendicular to the previous (4). Timely and spatial control of localization of the Z-ring assembly is most likely linked with chromosome segregation and DNA replication, involving proteins such as the nucleoid occlusion factor Noc, which ensures that the cells do not establish new septa across the chromosomes (5), and CcrZ, which connects initiation of DNA replication to cell division (6). The chromosomes and chromosome segregation also contribute to establish a physical barrier allowing the Z-ring only to be formed in an angle perpendicular to the previous division plane (4).…”