Poster abstracts
Poster number 134 submitted by Kiel Tietz
Examining 3’UTR interactions that promote rapid clearance of oscillating transcripts
Kiel T. Tietz (Molecular Genetics, The Ohio State University, Columbus), Thomas L. Gallagher, Nicolas L. Derr, Deepika Sharma, Zachary T. Morrow (Molecular Genetics, The Ohio State University, Columbus), Jasmine M. McCammon, Michael L. Goldrich (Molecular and Cell Biology, University of California, Berkeley, CA), Sharon L. Amacher (Molecular Genetics, The Ohio State University, Columbus)
Abstract:
Vertebrate segmentation is regulated by the segmentation clock, a biological oscillator that controls periodic formation of embryonic segments, or somites. This molecular oscillator generates cyclic gene expression in the tissue that will generate somites, called the presomitic mesoderm (PSM), and has the same periodicity as somite formation. Core molecular components of the segmentation clock include the hairy/Enhancer of split-related (her/Hes) family of transcriptional repressors, but additional transcripts such as ras homolog gene family member V (rhov) also cycle. Maintenance of clock oscillations requires that transcriptional activation and repression, RNA turnover, translation, and protein degradation are all very rapid as the clock cycles and a new somite pair forms every 30 minutes in the zebrafish embryo. We isolated a segmentation clock mutant, tortugab644, in which cyclic transcript oscillations are abnormal; mutant embryos express elevated levels of cyclic mRNAs such as her1 and rhov in the PSM. We have demonstrated that loss of Proline-rich nuclear receptor coactivator protein Pnrc2 is responsible for cyclic transcript accumulation in tortugab644 mutants. In human cell culture systems, Pnrc2 is implicated in mRNA decay by promoting decapping through interactions with Dcp1a and Upf1. Data from our lab support a similar decay function in zebrafish since antisense knockdown of pnrc2 and upf1 at low doses display a level of her1 transcript accumulation similar to tortuga, a phenotype not seen with either low dose pnrc2 or upf1 knockdown alone. We are also interested in cis-acting elements required for the rapid decay of oscillating transcripts. Our preliminary data support the hypothesis that the 3’UTR of cyclic mRNAs is important for Pnrc2-mediated decay since the her1 3’UTR confers instability to otherwise stable transcripts in vivo, in a Pnrc2-dependent manner. We are currently examining specific regions of the her1 3’UTR that are sufficient to induce rapid transcript decay to further define mechanisms responsible for the rapid turnover of oscillating transcripts.
Keywords: Pnrc2, her1, cyclic transcript