RNA splicing can serve as a mechanism of regulatory control by:
1. excising introns at different rates, thus speeding or slowing
the rate of protein
synthesis in the cytoplasm.
2. producing different proteins (isoforms
which have similar functions, but different
structures) by alternative splicing- exicing some exons and including others
during the modification of the pre-mRNA transcript.
Degradation of pre-mRNA can also serve a regulatory function. Only a fraction of the transcripts produced in the nucleus actually enter the cytoplasm as mature mRNA. The rest, either made at the wrong time, or by an innappropriate cell, are degraded in the nucleus.