A bifunctional snoRNA with separable activities in guiding rRNA 2'-O-methylation and scaffolding gametogenic effectors (direct RNA-Seq)
Small nucleolar RNAs (snoRNAs) are non-coding transcripts that guide chemical modifications of RNA substrates and contribute to gene expression at the epigenetic and post-transcriptional levels. However, the extent of their regulatory potential and the underlying molecular mechanisms remain poorly understood. Here, we identify a previously unannotated intronic C/D-box snoRNA, termed snR107, hosted in the fission yeast long non-coding RNA (lncRNA) mamRNA and carrying two independent cellular functions. On one hand, snR107 guides site-specific 25S rRNA 2'-O-methylation and promotes pre-rRNA processing/60S subunit biogenesis. On the other hand, snR107 associates with the gametogenic RNA-binding proteins Mmi1 and Mei2, mediating their reciprocal inhibition and restricting meiotic gene expression during sexual differentiation. Both functions require distinct cis-motifs within snR107, including a conserved 2'-O-methylation guiding sequence. Together, our results position snR107 as a dual regulator of rRNA modification and gametogenesis effectors, expanding our vision on the non-canonical functions exerted by snoRNAs in cell fate decisions. Overall design: To delineate the RNA species produced from the mamRNA-U14 locus in wild type cells, we conducted direct RNA sequencing using Oxford Nanopore Technology (ONT).