Abstract
Chromosome segregation is a crucial stage of the cell cycle. In general, proteins involved in this process are DNA-binding proteins, and in most bacteria, ParA and ParB are the main players; however, some bacteria manage this process by employing other proteins, such as condensins. The dynamic interaction between ParA and ParB drives movement and exerts positioning of the chromosomal origin of replication (oriC) within the cell. In addition, both ParA and ParB were shown to interact with the other proteins, including those involved in cell division or cell elongation. The significance of these interactions for the progression of the cell cycle is currently under investigation. Remarkably, DNA binding by ParA and ParB as well as their interactions with protein partners conceivably may be modulated by intra- and extracellular conditions. This notion provokes the question of whether chromosome segregation can be regarded as a regulatory stage of the cell cycle. To address this question, we discuss how environmental conditions affect chromosome segregation and how segregation proteins influence other cell cycle processes.
Highlights
Bacteria must adjust their cell cycle to their environmental conditions
While parAB genes were demonstrated to be essential in C. crescentus and M. xanthus, in a number of other bacterial species, including B. subtilis, P. aeruginosa, M. smegmatis, and C. glutamicum, elimination of ParA or ParB leads to chromosome segregation aberrations and mispositioning of the oriC region, eventually resulting in the formation of from 1 to 30% anucleate cells
Since DNA binding by ParA homologs may be influenced by intracellular ATP level, Soj likely links the changes of the cell physiological state and environmental conditions that have the impact on cell energetic state with the DnaA replication (Murray and Errington, 2008; Scholefield et al, 2011, 2012)
Summary
Bacteria must adjust their cell cycle to their environmental conditions. Unfavorable conditions such as starvation, oxidative, or osmotic stress alter the energetic state of the cell and trigger the stress signaling molecules (sigma factors, response regulators, signaling nucleotides) (Hengge, 2009; Gottesman, 2019; Latoscha et al, 2019; McLean et al, 2019). ParA and ParB are not fully widespread and chromosome segregation in some bacterial species (i.e., some γ-proteobacteria, including E. coli, which lack parAB genes) exploits the activities of other proteins, such as condensins (Nolivos and Sherratt, 2014; Dewachter et al, 2018).
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