Isolation of mutant alleles of the U6 snRNA m 6 A methyltransferase Mtl16 and characterization of their genetic interactions with splicing mutants in Schizosaccharomyces pombe.

Schizosaccharomyces pombe Dim1 is a conserved essential component of the U4/U6.U5 tri-snRNP complex essential for pre-mRNA splicing. In a synthetic lethal screen with the temperature-sensitive dim1-35 mutant, we isolated multiple alleles of non-essential mtl16 that encodes the U6 snRNA m 6 A methyltransferase. Further genetic analysis revealed strong and specific negative genetic interactions between mtl16 and a mutation in the Dim1 binding partner, Prp31, and between dim1-35 and a mutation in the Prp31 binding partner, Prp6. Our work provides additional tools to study pre-mRNA splicing in S. pombe and biological confirmation of the importance of the Prp6-Prp31-Dim1-U6 snRNA interactions for pre-mRNA splicing.