Poster abstracts
Poster number 148 submitted by Caleb Clark
Substrate recognition and function of the yeast ribonuclease Rnt1
Caleb Clark (OSU), Lee-Ann Notice-Sarpaning (UTHealth Houston), Ambro van Hoof (OSU)
Abstract:
RNA processing is required for proper gene expression in all domains of life. Saccharomyces cerevisiae ribonuclease III, or Rnt1, is an RNA processing endonuclease in the RNase III family, which is specific to dsRNA. Other family members include Drosha and Dicer. Rnt1, Drosha, and Dicer are all well-known ncRNA processing enzymes. However, we have recently shown that Rnt1 also degrades a subset of mRNAs, possibly as a quality control mechanism that degrades mRNAs that are inefficiently exported from the nucleus (Notice-Sarpaning, 2026, eLife). Most Rnt1 substrates share a predicted double-stranded stem with an AGNN loop which is thought to be an important determinant in Rnt1-mediated cleavage. The importance of the AGNN stem-loop has not been extensively tested in vivo. The most abundant substrate for Rnt1 is the pre-rRNA, which is cleaved in the 3’ external transcribed spacer. This cleavage is thought to be co-transcriptional and fast. Surprisingly, we found that mutation of the conserved AGNN sequence of the pre-rRNA substrate does not interfere with this processing, while complete deletion of the stem-loop does. This suggests that the conserved AGNN is not essential for target recognition, despite being a shared feature of Rnt1 substrates that is conserved across the Saccharomycetaceae family. Our findings also show that while rRNA is probably the most frequent substrate for Rnt1, this function contributes little to the growth phenotype of rnt1 mutants.
Keywords: RNA processing, rRNA, Ribonucleases