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Lecture 8

Lecture 8

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University of Toronto St. George
Jane Mitchell

Lecture 8 Transcription 21Structure of a gene2RNA polymerases3Transcription of protein coding genes4RNA processingAn expanded repertoire of RNAs to generateoIn eukaryotes we have RNA species which extend well beyond those normally required for simply production of polypeptidesoTo make all these different RNAs you also need different RNA polymerasesoIn bacterial system we focus on 1 single RNA polymerase but in eukaryotic system we focus on multiple RNA polymerases and they generate different types of RNAosnRNAs and snoRNAs have particular function involved in helping to process other RNAsforming secondary structures binding to those RNAs facilitating the splicing and reorganization of mRNAs or rRNAsoscaRNAs used to modify help splice reorganize snRNAs and snoRNAs which are then used to help splice the preRNAsomiRNAs and siRNAs are important in regulating gene expression They are being used by the cell at particular stages of post transcription or translation regulation by blocking either the translation of specific RNAs or by binding to existing RNAs through complimentary base pairingA number of eukaryotic RNA polymerases requiredoRNA polymerase 1 is involved in primarily in ribosomal RNA gene productionoRNA polymerase 3 is involved in tRNAsoEach of these RNAPs is a multisubunit proteinoEach is responsible for transcription of different sets of RNAsSubunits of eukaryotic RNA polymerasesoThe 5 subunit complexes beta beta alpha1 alpha2 omega are all you need to produce bacterial functional RNA polymeraseoVariety of other subunit complexes for eukaryotic RNA polymerasesoC terminal domain CTD is a little tail that extends out of the core of subunit 1 in RNA polymerase 2oSome subunits resemble the subunits of bacterial RNAPsEukaryotic vs bacterial RNA polymerasesoEukaryotic RNA polymerases require proteins to help position them at the promoter called transcription factorsoThese factors fulfill a similar role to the sigma subunit of the bacterial RNA polymerasesoThe reason for these factors is because eukaryotic RNA polymerases need to deal with chromosomal structuresGene structureoProkaryotic mRNA use polycistronic message to produce 3 proteins in this caseoEukaryotic mRNA dont encode more than a single gene within that mRNA but they also require significant amount of processingoIt involves things such as addition of cap structures PolyA tails etcTranscription of proteincoding genesoPromotersoInitiation of transcriptionoRNA processingPromotersoPromoters are the consensus sequences that are found in the genomic DNA which are recognized by transcription factors and they initiate the process such that the RNA polymerase can wind up in the correct spotoTF2B transcription factor RNA polymerase 2 B
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