Project Summary/Abstract There is a fundamental gap in our understanding of how helicobacter pylori (Hp), a bacterium that is highly relevant to public health, regulates its life cycle. Although mechanistic details of how Hp induces damage to host cells have been revealed, our understanding for how this pathogen regulates its own proliferation remains unclear. The existence of this knowledge gap represents a burden in the need to develop novel specie-specific drugs that can control the proliferation of Hp in human patients. Our long-term goal is to identify drug targets that are essential in regulating Hp cell cycle and proliferation. The overall objective of the proposed research is to define the regulatory circuitry that controls the forward progression of Hp cell cycle. Our central hypothesis is that the chromosome replication initiator DnaA in Hp is a central node connecting multiple cell cycle regulating factors. DnaA is a multifunctional protein that aside from opening the chromosomal region known as the origin of replication (ori), it also acts as a highly regulated transcription factor. The rationale for the proposed research is that DNA replication initiators have been shown to influence the activity of other cellular machines involved in the cell cycle, such as cytokinesis, cell growth, and cellular development. Our plan is to test our central hypothesis, and thus accomplish our overall objective for this project, by pursuing the following three specific aims: 1) Define the DnaA transcriptional regulon by analyzing the global chromosome profile of promoters bound by DnaA using chromatin immunoprecipitation assays followed by deep sequencing; 2) Identify regulators that modulate DnaA's activity at the origin of replication by cross-linking and isolating the chromosomal ori-proteins complex using a DNA-sampling technique; 3) Identify factors that directly interact with DnaA by isolating DnaA-containing protein complexes within the cell. Successful completion of the proposed research is expected to vertically advance and expand our knowledge of and ability to assemble the regulatory circuitry that controls Hp cell cycle. Furthermore, findings from our work will broaden our understanding of how the highly conserved replication initiators coordinate DNA synthesis with the progression of the cell cycle. Our proposed research is innovative, in our opinion, because it represents a substantive departure from the status quo by targeting Hp-specific cell cycle regulators as targets for new antibiotics.