Fumeaux, CoralieRadhakrishnan, Sunish KumarArdissone, SilviaThéraulaz, LaurenceFrandi, AntonioMartins, DanielNesper, JuttaAbel, SörenJenal, UrsViollier, Patrick H.2014-08-132014Fumeaux, Coralie, Sunish Kumar Radhakrishnan, Silvia Ardissone, Laurence Théraulaz, Antonio Frandi, Daniel Martins, Jutta Nesper, Sören Abel, Urs Jenal, and Patrick H. Viollier. 2014. “Cell cycle transition from S-phase to G1 in Caulobacter is mediated by ancestral virulence regulators.” Nature Communications 5 (1): 4081. doi:10.1038/ncomms5081. http://dx.doi.org/10.1038/ncomms5081.2041-1723http://nrs.harvard.edu/urn-3:HUL.InstRepos:12717475Zinc-finger domain transcriptional regulators regulate a myriad of functions in eukaryotes. Interestingly, ancestral versions (MucR) from Alpha-proteobacteria control bacterial virulence/symbiosis. Whether virulence regulators can also control cell cycle transcription is unknown. Here we report that MucR proteins implement a hitherto elusive primordial S→G1 transcriptional switch. After charting G1-specific promoters in the cell cycle model Caulobacter crescentus by comparative ChIP-seq, we use one such promoter as genetic proxy to unearth two MucR paralogs, MucR1/2, as constituents of a quadripartite and homeostatic regulatory module directing the S→G1 transcriptional switch. Surprisingly, MucR orthologues that regulate virulence and symbiosis gene transcription in Brucella, Agrobacterium or Sinorhizobium support this S→G1 switch in Caulobacter. Pan-genomic ChIP-seq analyses in Sinorhizobium and Caulobacter show that this module indeed targets orthologous genes. We propose that MucR proteins and possibly other virulence regulators primarily control bacterial cell cycle (G1-phase) transcription, rendering expression of target (virulence) genes periodic and in tune with the cell cycle.en-USJournal Article2014-08-1310.1038/ncomms5081