Poster abstracts

Poster number 28 submitted by Khyati Shah

Examining the regulation, composition and function of ribonucleoprotein (RNP) granules in quiescent cells

Khyati H Shah (Dept. of Molecular Genetics, The Ohio State University), Paul K Herman (Dept. of Molecular Genetics, The Ohio State University)

Abstract:
In response to stress, eukaryotic cells accumulate specific mRNAs and proteins at discrete sites or foci in the cytoplasm. Two of the best characterized of these RNP foci, P bodies (PBs) and stress granules (SGs), contain translationally-repressed mRNAs and a partially overlapping set of protein constituents. Although these RNP granules have been conserved through evolution, the mechanisms regulating their formation, and the roles they play during these periods of stress, are not yet understood. Interestingly, our work with PBs in Saccharomyces cerevisiae has provided insight into both of these issues. First, we have found the cAMP dependent protein kinase (PKA) is a key regulator of PB assembly. Second, our work indicates that the presence of PB foci is essential for the long-term survival of stationary phase cells. Both PBs and SGs are present in these quiescent cells. To begin to address the role PBs play in stationary phase, we set out to identify the protein constituents of these RNP foci. Here, I will present the results of a localization screen conducted with the entire set of protein kinases and phosphatases in S. cerevisiae. These studies show that ~25% of these signaling molecules localize to discreet cytoplasmic foci during stationary phase entry. Several of these proteins, including an essential casein kinase 1 isoform, localize specifically with PBs whereas other kinases are found with either SGs or novel foci that have not before been identified. Altogether, these results suggest that there is widespread reorganization of key signaling molecules upon nutrient starvation. Defining the physiological consequences of these protein relocalization events should provide important insight into the biological roles played by these RNP foci and how these activities impact the survival of quiescent cells.

References:
1) Shah KH, Zhang B, Ramachandran V, Herman PK. Processing body and stress granule assembly occur by independent and differentially regulated pathways in Saccharomyces cerevisiae.Genetics. 2013 Jan;193(1):109-23
2)Ramachandran V, Shah KH, Herman PK.The cAMP-dependent protein kinase signaling pathway is a key regulator of P body foci formation.Mol Cell. 2011 Sep 16;43(6):973-81.

Keywords: P-bodies, Stress Granules, quiescence