Poster abstracts

Poster number 48 submitted by Ulf-Peter Guenther

Function of the DEAD-box RNA helicase Ded1p in translation initiation

Ulf-Peter Guenther (RNA Center, Case Western Reserve University), Frank Tedeschi (RNA Center, Case Western Reserve University), Eckhard Jankowsky (RNA Center, Case Western Reserve University)

Abstract:
The highly conserved and essential DEAD-box helicase Ded1p is critical for translation initiation in Saccharomyces cerevisiae. To understand how molecular function of Ded1p corresponds to its role in translation initiation we used a temperature-sensitive Ded1p mutation that causes slow growth at elevated temperatures. This mutation lowers affinity of Ded1p to RNA and alters the kinetic response of translation initiation to mild heat shock (30^oC to 37^oC). RNA-seq of the translated mRNA pool shortly after heat shock shows that the RNA binding defect in Ded1p impacts translation initiation for most mRNAs. Translation initiation is decreased for roughly 1/3 of the affected mRNAs, and increased for the remaining 2/3. The largest decrease is seen for mRNAs encoding proteins involved in mRNA metabolism. We further show that Ded1p binds to a large cross-section of mRNAs, consistent with functional effects on a broad range of mRNAs. Ded1p binds mRNAs at multiple sites that do not show obvious sequence or structure signatures. However, the pattern of Ded1p binding differs between more and less affected mRNAs. Collectively, our data indicate that Ded1p is a general translation initiation factor that affects translation initiation of virtually all RNAs. However, the magnitude of the effects corresponds to the binding pattern of Ded1p to a given mRNA.

Keywords: RNA helicase, translation initiation, RNA binding