mRNA splicing, via spliceosome mRNA cis splicing, via spliceosome GO:0045292 nuclear mRNA cis splicing, via spliceosome nuclear mRNA cis splicing, via U2-type spliceosome biological_process The joining together, after removal of an intervening sequence composed of one or more introns, of two segments of the same RNA molecule via spliceosomal catalysis to produce an mRNA composed only of exon sequences that all came from the same primary transcript. splicing