mRNA Splicing Transport of Mature Transcript to Cytoplasm mRNA 3'-end processing Formation of pre-mRNPs Internal Methylation of mRNA Processing of Capped Intron-Containing Pre-mRNA Authored: Carmichael, GG, Hammarskjold, ML, Hastings, M, Krainer, AR, Marzluff, WF, Wahle, E, Zhang, Z, 2003-06-05 08:30:31 Co-transcriptional pre-mRNA splicing is not obligatory. Pre-mRNA splicing begins co-transcriptionally and often continues post-transcriptionally. Human genes contain an average of nine introns per gene, which cannot serve as splicing substrates until both 5' and 3' ends of each intron are synthesized. Thus the time that it takes for pol II to synthesize each intron defines a minimal time and distance along the gene in which splicing factors can be recruited. The time that it takes for pol II to reach the end of the gene defines the maximal time in which splicing could occur co-transcriptionally. Thus, the kinetics of transcription can affect the kinetics of splicing.Any covalent change in a primary (nascent) mRNA transcript is mRNA Processing. For successful gene expression, the primary mRNA transcript needs to be converted to a mature mRNA prior to its translation into polypeptide. Eucaryotic mRNAs undergo a series of complex processing reactions; these begin on nascent transcripts as soon as a few ribonucleotides have been synthesized during transcription by RNA Polymerase II, through the export of the mature mRNA to the cytoplasm, and culminate with mRNA turnover in the cytoplasm. Edited: Gillespie, ME, Gopinathrao, G, Joshi-Tope, G, 0000-00-00 00:00:00 Reactome Database ID Release 4372203 Reactome, http://www.reactome.org ReactomeREACT_125 Reviewed: Nilsen, TW, 0000-00-00 00:00:00 PathwayStep70 PathwayStep48 PathwayStep51 PathwayStep30 PathwayStep31