Faithin Omaha eBook Collection

Download or read book Analysis of an Uncharacterized Gene in Caulobacter Crescentus and Its Novel Connections with Cell Cycle Regulatory Machinery written by Haibi Wang and published by . This book was released on 2019 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cell division and differentiation are complex biological phenomena that occur in all kingdoms of life. Understanding the molecular mechanisms that underlie these complex processes often requires the study of experimentally tractable model organisms. As a Gram-negative bacteria with less than four thousand genes, Caulobacter crescentus exhibits cell differentiation, highly regulated chromosome replication and segregation, and asymmetric cell division with every turn of the cell cycle. To achieve these behaviors, Caulobacter utilizes spatial control mechanisms such as sub-cellular compartmentalization and protein localization. The cell poles are particularly enriched for cell cycle regulatory proteins. Many of these proteins are localized by the hub protein PopZ, which forms a three-dimensional scaffold that also aids in chromosome segregation. The PopZ scaffold also includes proteolysis activity, which regulates cell cycle progression in a manner that is analogous to well-known eukaryotic systems. In this dissertation, I characterized an evolutionarily conserved protein of unknown function, which is now named SpbR (Swarmer pole blocking factoR). SpbR is a pole-localized protein that has co-evolved with PopZ and other polar proteins. Strikingly, SpbR over-production exhibited a severe chromosome segregation phenotype, in which the newly replicated centromere failed to travel across the cell to its normal destination at the opposite pole. SpbR overproduction results in its accumulation at the old pole, where it physically interacts with PopZ. This prevents the relocation of PopZ to the new pole, thereby eliminating a positional cue for centromere translocation. Consistent with this, the centromere translocation phenotype of SpbR overproducing cells is further enhanced in genetic backgrounds that accumulate higher SpbR or reduce chromosome segregation activity. We find that pole-localized SpbR is normally cleared by proteolysis before the time of chromosome segregation, indicating that SpbR turnover is part of the cell cycle-dependent program of polar development.