Lecture 22 done

Lecture 22 done - Lecture 22 Study Questions 1. Eukaryotes...

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Lecture 22 Study Questions 1. Eukaryotes can regulate gene expression at 2 global stages between transcription and translation; which are they? RNA processing and RNA transport to cytoplasm. RNAs that differ in length from original transcript. 2. In which compartment of the cell does RNA processing take place? Nucleus 3. What are the 4 major steps/processes during maturation of pre-mRNAs into mRNAs? 1)“capping”, 2) 3’-end cleavage (by endonuclease), 3)polyadenylation (by poly A polymerase +ATP) precursor mRNA still can not be translated, 4) Splicing (excision of pre-mRNA introns) introns are removed because that do not code for any proteins 4. What is the mRNA cap? Draw its structure. What are its 4 functions? When is it added? -Capping occurs during transcription; occurs at transcription because it interaces with RNA-processing factors (Pol II); -Modifications that result in the addition of a 7-methylguanosine via 5’- 5’triphosphate linkage to the 5’-end of pre-mRNA and the methylation of the first 1-2 nucleotides at the 2’-OH position of the ribose. Functions: 1) stabilizes mRNA against degradation 2) stimulates splicing of pre-mRNAs (via CAP-binding nuclear proteins) 3) helps mRNA transport to cytoplasm (bound by nuclear proteins that export mRNAs) 4) stimulates translation initiation of mRNA by binding eukaryotic translation initiation factors (i.e. CAP) 5) How is capping coupled to transcription of pre-mRNAs?
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Capping marks RNA molecules as mRNA precursors and serves to protect them from RNA digesting enzymes in the nucleus. Considerable evidence indicates that capping of the nascent transcript is coupled to elongation by RNA polymerase II so that all of its transcripts are capped during the earliest possible phase of elongation. Capping allows RNA polymerase II to enter into a faster mode of elongation that rapidly transcribes away from the promoter. Polymerase waits for
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Lecture 22 done - Lecture 22 Study Questions 1. Eukaryotes...

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