1/ 🔬 Our work, "Dynamic transitions of initiator binding coordinate the replication of the two chromosomes in Vibrio cholerae", is now published in Nature Communications.
Here's a thread on how we think Chr1 and Chr2 replication is coordinated in Vibrio. 🧵
Link : https://www.nature.com/articles/s41467-024-55598-9
Here's a thread on how we think Chr1 and Chr2 replication is coordinated in Vibrio. 🧵
Link : https://www.nature.com/articles/s41467-024-55598-9
Comments
Vibrio cholerae has two chromosomes, Chr1 and Chr2, that must replicate in sync to ensure genome stability. A checkpoint sequence on Chr1, crtS, triggers replication of Chr2. This study examines how this precise coordination is achieved.
To investigate this mechanism, we mapped the binding of RctB (the initiator for Chr2 replication) across the genome at different points in the cell cycle using ChIP-seq. This was combined with live-cell microscopy, transmission electron microscopy and structural studies.
ChIP-seq revealed that RctB binds to inhibitory sites (29/39m) on Chr2’s origin, blocking Chr2 replication for most of the cell cycle. Using TEM, we observed how RctB forms large nucleoprotein complexes at ori2. These complexes bridge 29/39m sites, creating loops.
Cryo-EM and X-ray crystallography revealed that RctB oligomerizes through two key interfaces in its domain IV, enabling the formation of higher-order complexes that stabilize the inhibitory DNA loops at ori2.
After crtS is replicated on Chr1, RctB shifts to activation sites (iterons), unlocking Chr2 replication. Each crtS replication event triggers replication of a single ori2. This ensures a precise one-to-one synchronization between Chr1 and Chr2.
Before crtS replication: ori2 is OFF, blocked by inhibitory RctB-DNA loops.
After crtS replication: inhibition is destabilized, ori2 becomes accessible, and Chr2 replication begins.
A beautiful molecular ON/OFF switch! 🕹️