Poster abstracts
Poster number 153 submitted by Kiel Tietz
Pnrc2 regulates 3’UTR-mediated decay of cyclic transcripts during somitogenesis
Kiel T. Tietz (Department of Molecular Genetics, The Ohio State University), Thomas L. Gallagher, Nicolas L. Derr, Zachary T. Morrow, Sharon L. Amacher (Department of Molecular Genetics, The Ohio State University)
Abstract:
Vertebrate segmentation is regulated by the segmentation clock, a biological oscillator that controls periodic formation of embryonic segments. This molecular oscillator generates cyclic gene expression in the tissue that generates somites and has the same periodicity as somite formation. Molecular components of the clock include the her/Hes family of transcriptional repressors, but additional transcripts also cycle. Maintenance of clock oscillation requires that transcriptional activation and repression, RNA turnover, translation, and protein degradation are rapid (one cycle is 30 minutes in the zebrafish). We previously isolated a zebrafish segmentation clock mutant, tortuga, that has elevated levels of cyclic transcripts. We show that loss of proline-rich nuclear receptor coactivator protein Pnrc2 is responsible for cyclic transcript accumulation in tortuga deletion mutants and that a new pnrc2 loss-of-function mutant displays an identical phenotype. pnrc2 mRNA is maternally provided and zygotically expressed, and in maternal-zygotic pnrc2 mutants, cyclic transcripts perdure even longer. We show that the her1 3’UTR confers instability to otherwise stable transcripts in a Pnrc2-dependent manner, and that tethering Pnrc2 to the 3’UTR of a stable transcript triggers rapid decay, indicating that the 3’UTR of cyclic transcripts is critical for Pnrc2-mediated decay. Knockdown of pnrc2 in a validated transgenic cyclic reporter line, Tg(her1:her1-Venus), causes reporter transcript accumulation, yet reporter protein is expressed normally. Endogenous cyclic protein also does not accumulate in pnrc2 mutants, suggesting that stabilized cyclic transcripts are not efficiently translated and perhaps are controlled by an additional post-transcriptional mechanism. Our work explores these post-transcriptional mechanisms regulating oscillation dynamics during somitogenesis and will further our understanding of other ultradian oscillators in general.
Keywords: Pnrc2, oscillating transcripts, mRNA decay