BIO315H5 Chapter Notes - Chapter 6: Nonsense-Mediated Decay, Exon Junction Complex, Molten Globule
Document Summary
Bio315 chapter 6 p351-362 mrna production requires transcription + rna processing steps take place in nucleus and when processing is completed, mrna is transported to cytosol to be translated. Not foolproof, sometimes incorrectly processed mrnas are sent or good mrna can get broken. To avoid translating bad mrna 5" cap + poly a tail are recognized. Nonsense mediated decay mrna surveillance system eliminates bad mrna before they can leave nucleus detects nonsense codon (premature stop codon) in the wrong place. Happens when mrna is improperly spliced where random stop codons are introduced. Begins: mrna is transported from nucleus to cytosol as 5" end emerges from nuclear pore, mrna is met by ribosome which translates it. As translation starts, exon junction complex bound to the mrna at splice site is replaced by ribosome. The normal stop codon will be after the last exon so by the time reaches that stop codon, there are no more ejcs passes inspection.
