KB sites engaged, so the general transcription apparatus is set up at the transcription start site. RNA pol II fires off transcription of that gene to make pre mRNA. AAUAA sequence at 3’ end allows recognition and termination of transcription. Now we have a pre mRNA that needs 3 modifications
Methyl 7G cap on 5’ end. Spliceosomes made up of SNRPs cut out introns and join the exons together via RNA that acts as a catalytic RNA. A AAA tail is added on the 3’ end. Now we have a mature mRNA in nucleus that is then transported into the cytosol.
The mRNA M7G cap is recognized and scanned by the small rRNA for the AUG start codon. tRNA carrying the anticodon for AUG binds at P site is brought to the A site, and translocation of the methionine ejects the tRNA. The peptide carries a KDEL sequence that causes translation to stop when it is recognized by the signal recognition particle. The entire complex is moved to the RER. Here, the signal recognition particle is released by the hydrolysis of GTP to GDP,