BIOL-L211 Lecture 21 Outline of Last Lecture I. Major Differences in Transcription in EukaryotesII. Transcriptional Control of a Eukaryotic GeneIII. Transcription Initiation in EukaryotesIV. Elongation in Eukaryotes Outline of Current Lecture I. FACTII. RNA ProcessingIII. PolyadenylationCurrent LectureTranscription in Eukaryotes I.5(For a refresher on the nucleosome: see 9.10.14 Lecture)I. FACTA. Facilitates Chromatin TranscriptionB. Allows elongation to proceed despite chromatinC. Heterodimer (hetero = different; dimer = 2): Spt16 and SSRP11. Spt16 binds to the H2A and H2B dimer (recall nucleosome) *remember H1 is the linker histonea. Spt16 removes one dimer ahead of Pol IIb. Elongation continuesc. Dimer replacedThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. SSRP1 binds to the H3 and H4 tetramer3. SPT6 (not actually part of FACT) helps reassemble the nucleosomeII. RNA ProcessingA. Processing Factors1. Phosphorylated CTD tail recruits RNA processing factors to Pol II2. Factors are transferred to RNA as needed3. Tail is capped as soon as the transcript emerges from Pol IIB. Capping1. Formation of 5' cap2. 5' cap = methylated guanine on 5' end of RNA3. Process:a. RNA triphosphatase is responsible for removing a gamma phosphate from the 5' end of RNAb. The beta and gamma phosphates are removed from guaninec. Guanylyltransferase transfers a guanine to the 5' beta phosphate of the RNA strandd. Methyltransferase does what it always does: ADDS METHYL GROUPSi. The groups are added to the guanineii. The end of RNA won't degrade with the capiii. Methyl group is a signal to the ribosomes to bind for translationIII. PolyadenylationA. CTD tail recruits enzymes necessary for polyadenylationB. After Poly-A tail is transcribed, the enzymes transfer to the RNA strandC. Enzymes:1. CstF: stimulates cleavagea. Binds mRNAb. Cleaves mRNA into two piecesc. The shorter piece will be degradedd. The non-degraded piece will be modified at the 3' end2. CPSF: specifies cleavages and polyadenylationa. Binds to mRNA @ poly-A signalb. Responsible for recruitment of Poly-A Polymerase (TBA)D. Poly-A Signal: transcribed trigger for the transfer of polyadenylation enzymes from the CTD tail to RNA-Lecture cut off
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