Biochemistry 2280A Lecture Notes - Lecture 24: Protozoa, Chloroplast, Spliceosome
23 Apr 2016
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Topic 24: formation of mrnas: pre-mrna mrna. 5" capping, 3" polyadenylation, splicing are all concerted processes (meaning that they happen together at the same time as transcription) and each requires a specific enzyme. Primary transcript must become mrna for export out of the nucleus. When rna is first made, it begins with a triphosphate (5") i. e. upon synthesis, the first base is a triphosphate. 7-methylguanosine (fig 7-16): there is a 5"-5" linkage between the 5" end of primary transcript and the 7- methylguanosine (5" cap). The 5" cap marks that the mrna is intact for translation. If an rna does not have a 5" cap, it is not an intact mrna. 5" cap is also required for mrna export from the nucleus and translation of the mrna into protein (i. e. 5" cap acts as a translation signal). Without the 5" cap, it will not be exported or translated. the bunch of aa tails.
