DETERMINE THE IN VIVO TARGETS FOR THE ACETYLTRANSFERASE ACTIVITY OF ELP3P

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our lab has had a long-standing interest in understanding the molecular events underlying the activation of Rab proteins in membrane traffic, and we recently isolated the yeast homolog of IKAP, Elp1p, via a genetic screen to identify factors regulating Rab GTPase action. The FD syndrome protein is found in a complex with five other proteins, termed the Elongator complex. Our studies revealed an essential cytoplasmic role for the Elp complex in the regulation of polarized exocytosis [1]. Mutations in the human ELP1 gene are a cause of the neurological disorder Familial Dysautonomia. The long-term goal of the research is to elucidate the mechanism of the FD disease syndrome protein and the pathway leading from IKAP dysregulation to the clinical presentation. The project proposed here is directed at understanding the molecular mechanisms by which Elp1p and the Elongator complex regulate polarized secretion and growth. The most highly conserved subunit of the Elp complex is Elp3p and this is also the only subunit with a primary sequence suggestive of catalytic functions, with a Radical SAM and acetyltransferase domain. Having described the phenotypic output of the Elp complex, we are interested in understanding its mechanism of action, which is likely to be through its enzymatic activities. Previous work from this laboratory has shown that mutation of the acetyltransferase (AT) domain of Elp3p can suppress mutations in the late secretory pathway of yeast [1], suggesting that the catalytic activity is necessary for the negative regulation of secretory traffic by the Elp complex. Extrapolating from this result, we hypothesize that Elongator may act to post-translationally regulate protein activities via acetylation. This project is part of a larger effort to identify potential targets acetylated by the Elp complex. 1. Rahl, P.B., Chen, C.Z. and Collins, R.N. (2005) Elp1p, the yeast homolog of the FD disease syndrome protein, negatively regulates exocytosis independently of transcriptional elongation. Molecular Cell 17:841-853