condensates with mediator and RNA Pol II to initiate transcription o

Condensates with mediator and rna pol ii to initiate

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condensates with mediator and RNA Pol II to initiate transcription o Chromosomes enter droplet containing all the elements required for transcription Explains how you can have transcriptional bursts on two different chromosomes at the same time lect. 23 – RNA Processing I RNA Pol II CTD - CTD is full of repeats: YSPTSPS (x52 in humans) - C-terminal domain = highly disordered - TFIIH protein kinase is responsible for the phosphorylation of the 2 nd S (Ser5) in the CTD repeats - Another protein kinase is responsible for phosphorylation of 1 st S (Ser2) Phosphorylation of the C-terminal domain (CTD) of RNA Pol II large subunit - Transcriptional initiation: o Pol II is on the promoter o DNA helicase opens the transcription complex o TFIIH phosphorylates the CTD on ser5 so that RNA Pol II can leave the promoter o RNA Pol II switches to elongation phase and leaves the promoter begins elongation and extends the chain - Pol II stops at the first nucleosome after the promoter: o Pausing is important as a quality check before starting full elongation o Need to protect the mRNA product from digestion protect 5’ end of mRNA by the addition of a 7-methyl-guanylate cap 1. TFIIH protein kinase phosphorylates ser5 in CTD RNA Pol II switches to elongation phase and leaves the promoter 2. RNA Pol II pauses soon after leaving the promoter 3. Ser5-phosphorylation recruits the capping enzyme
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4. Capping enzyme caps the 5’ end of the mRNA product with a 7’ methyl-guanylate cap through a 5’-5’ triphosphate linkage , 1 st and 2 nd base are also methylated a. Protects the pre-mRNA b. Facilitates nuclear transport c. Allows recognition by translation factors 5. P-TEFb protein kinase phosphorylates ser2 in CTD full elongation and finishing transcription a. Recruits in new factors for RNA processing in CTD b. Releases negative elongators 2 phosphorylation events occur and are mediated by 2 protein kinases Proteins bind to RNAs - Proteins protect or mediate effects on RNA - Interactions mediated by specific domains - RNA + Protein = ribonucleoprotein complex (RNP) o RRM domain: impart the ability to interact with RNAs o KH domains, RGG repeats interaction of protein & RNA Pre-mRNA mRNA: splicing - Eukaryotic genes have big introns - Introns get spliced out of the pre-mRNA transcript and only exons are present in the mature mRNA - Introns have evolved regulatory elements often in DNA that encodes introns - Exons code for proteins or are in 5’ & 3’ UTRs Introns - Discovered due to the difference in mRNA size and gene size & visualized by hybridization experiments - Branch-point adenosine is near the pyrimidine-rich region & is 100% conserved - Intron borders are highly conserved o 3’ splice site = AG
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o 5’ splice site = GU o Branch point = A - Conserved splice sites of introns are recognized by small nuclear RNAs (snRNAs) in the spliceosome Spliceosome functionality: snRNAs - Spliceosome is responsible for splicing out introns o Consists of 5 snRNPs (small nuclear ribonucleoprotein particles) o snRNPs consist of an snRNA (U1, U2, U3, U4, U5 or U6) + 6-10 proteins -
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