A bifunctional snoRNA with separable activities in guiding rRNA 2'-O-methylation and scaffolding gametogenic effectors (meiosis 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. To determine the expresion dynamics of meiotic mRNAs during sexual diferentiation in wild type and snR107kloopmut cells, we conducted RNAseq experiments at different time points following induction of synchronized meiosis by adding 3-MB-PP1 to the cultures to chemically inactivate the analogous-sensitive allele of the Pat1 kinase (pat1-L95G).