Methyltransferases that modify spliceosomal small nuclear RNAs (snRNAs) play an important role in the cell, ensuring the correct maturation of snRNAs, which, in turn, is necessary for the optimal functioning of the spliceosome. In this work, we studied the enzyme METTL4, which performs N6-methylation of 2′-O-methyladenosine at position 30 of U2 snRNA. The function of both the protein and the modification in splicing is currently unclear. We showed that inactivation of METTL4 gene in HeLa S3 cells results in significant change in alternative splicing, a general slowing of splicing and accumulation of introns. In cells without METTL4, the expression of genes associated with the maturation of ribosomal RNA is decreased, and in the nuclei of these cells the number of coilin-positive structures, most likely Cajal bodies, is reduced.
Bolikhova et al. (Wed,) studied this question.