RNA processing
After transcription in the nucleus and before translation into a protein in the cytoplasm, newly transcribed RNA undergoes post-transcriptional modifications to become the mature mRNA. These modifications include the addition of a 5'cap and 3'poly A tail, and splicing out of noncoding introns. These modifications are needed for the RNA molecule to be protected against RNase activity as well as for it to be recognized by molecules that mediate translation into proteins. Splicing of the RNA is required to remove the portions of the message that are not supposed to be translated into the final protein product. In addition to intron and exon splicing of the pre-mRNA, ~70% of pre-mRNAs in C. elegans are trans-spliced to one of two different splice leader sequences, SL1 or SL2.