Spliceosomal proteins direct RNA methylation to modulate gene expression and silence retrotransposons [RNA-seq]

Using genetic screening and biochemical analyses in S. pombe, we identified the RNA methyltransferase Tgs1 as a component of a protein complex called TEaM, which is specifically recruited by spliceosomal proteins to transcripts containing inefficiently spliced cryptic introns.

Strikingly, the presence of cryptic introns alone can trigger TEaM-dependent silencing of stress-inducible genes and repetitive elements, including retrotransposons, while Tgs1 is also directed to gametogenic transcripts via a YTH-domain RNA-binding protein. In both contexts, Tgs1 catalyzes trimethylguanosine (TMG) capping, a modification that recruits the conserved Pir2/ARS2 protein and promotes RNA processing through the RNAi pathway.