Intron removal from pre-mRNA is called
Removal of noncoding introns from precursor messenger RNA and ligation of coding exons is termed splicing, essential step generating continuous open reading frame for translation. Carried out by spliceosome, dynamic ribonucleoprotein complex assembling on consensus signals GU at five prime splice site, branch point adenosine near three prime end, and AG at three prime splice site. Two transesterification reactions without ATP for chemistry, ATP used for helicase remodeling, excise intron as lariat and join exons. Alternative splicing produces multiple isoforms from single gene expanding proteome complexity in metazoans significantly.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 6: Intron removal called splicing; Lodish 9th ed., Pre-mRNA splicing overview