Proper spatial and temporal regulation of the cell cycle is crucial to the survival and proliferation of all organisms. To ensure stable, orderly cell cycle progression, cells employ complex genetic circuits. The architecture, operation, and design principles of such circuits remain only poorly understood. The bacterium Caulobacter crescentus provides an experimentally tractable system for studying genetic circuits and for elucidating fundamental molecular mechanisms of cell cycle regulation. In C. crescentus the cell cycle is driven by the periodic rise and fall in activity of a master regulator, CtrA. Active CtrA directly regulates the expression of nearly 100 genes, many of which coordinate cell division. CtrA also directly binds to and silences the origin of replication. Cell cycle progression therefore requires oscillations in CtrA activity - it must be cleared from the cell to permit DNA replication, but must accumulate to drive cell division. The outline of a genetic circuit controlling CtrA is in place, but does not yet fully account for the dynamics of CtrA activity. Additional components and levels of regulation must exist. The goal of this project is to define the complete molecular circuitry that controls CtrA activity and hence ensures orderly progression through the cell cycle. To this end, we will: (i) map the pathways that regulate phosphorylation and dephosphorylation of CtrA, (ii) elucidate how cells control the sub-cellular localization and activity of CckA, the primary phosphodonor for CtrA (iii) examine how multiple transcriptional feedback loops collaborate to precisely control the induction dynamics of CtrA, and (iv) identify and characterize additional factors that regulate CtrA activity. These studies will help to unveil how cells use multiple modes of regulation to successfully navigate their cell cycle. In addition, this work will help to reveal the general design and operating principles of genetic circuits, which underlie regulatory processes throughout biology. Finally, a better understanding of how bacteria regulate the cell cycle may help guide the development of new antibiotics, a problem of increasing public-health relevance.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM082899-05
Application #
8245739
Study Section
Prokaryotic Cell and Molecular Biology Study Section (PCMB)
Program Officer
Hamlet, Michelle R
Project Start
2008-04-01
Project End
2013-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
5
Fiscal Year
2012
Total Cost
$288,032
Indirect Cost
$111,614
Name
Massachusetts Institute of Technology
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
001425594
City
Cambridge
State
MA
Country
United States
Zip Code
02139
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Jonas, Kristina; Chen, Y Erin; Laub, Michael T (2011) Modularity of the bacterial cell cycle enables independent spatial and temporal control of DNA replication. Curr Biol 21:1092-101

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