SMC Progressively Aligns Chromosomal Arms in Caulobacter crescentus but Is Antagonized by Convergent Transcription

Publication date: 29 August 2017
Source:Cell Reports, Volume 20, Issue 9
Author(s): Ngat T. Tran, Michael T. Laub, Tung B.K. Le
The structural maintenance of chromosomes (SMC) complex plays an important role in chromosome organization and segregation in most living organisms. In Caulobacter crescentus, SMC is required to align the left and the right arms of the chromosome that run in parallel down the long axis of the cell. However, the mechanism of SMC-mediated alignment of chromosomal arms remains elusive. Here, using genome-wide methods and microscopy of single cells, we show that Caulobacter SMC is recruited to the centromeric parS site and that SMC-mediated arm alignment depends on the chromosome-partitioning protein ParB. We provide evidence that SMC likely tethers the parS-proximal regions of the chromosomal arms together, promoting arm alignment. Furthermore, we show that highly transcribed genes near parS that are oriented against SMC translocation disrupt arm alignment, suggesting that head-on transcription interferes with SMC translocation. Our results demonstrate a tight interdependence of bacterial chromosome organization and global patterns of transcription.

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Teaser

Tran et al. investigate the mechanism and function of SMC in the global organization of the Caulobacter chromosome. The findings suggest that SMC functions as a tether to actively cohese the chromosomal arms together and show that head-on transcription profoundly interferes with SMC translocation from the centromeric parS site.


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