Topic 29, termination of transcription, RNAi.ppt.edu

Topic 29, termination of transcription, RNAi.ppt.edu -...

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Topic 29: Transcriptional termination and RNA interference
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Learning objectives Be able to define the following terms: UTR, polyadenylation signal, polyadenylation site, RNA interference, miRNA, shRNA, siRNA, guide strand, DICER, R2D2, Argonaute Be able to describe the major events of transcriptional termination in eukaryotes , including the ability to distinguish between the 2 current models for how it occurs (slides 9-10) Be able to diagram the organization of the sequence elements at the 3’ end of pre-mRNA that are involved in termination (slide 5) Be able to describe the purpose of RNA interference and how we can manipulate the process for therapeutic benefit And describe the major components & processes of the pathway (slides 15- 19)
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Transcriptional termination 3 general steps: Cleavage of pre-mRNA at poly(A) site Addition of poly(A) tail Termination of transcription & removal of RNA polymerase
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All mRNAs have 5’ and 3’ regions that are not translated (called non-coding or untranslated regions/UTRs) --If there is a sequence of mRNA that is not translated at the beginning, then how does the ribosome know where to start? 5’ cap 3’ poly-A tail 5’ UTR (UTR) (UTR) 3’ UTR Start codon Stop codon Open Reading Frame (ORF) defined by start and stop codons
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Figure 17.40a: Poly(a) site recognition in mammals. Learn the regions and sequences in red boxes Site that is initially recognized; required for cleavage and poly(A) addition Site that is cut; tail is added to new end --No consensus sequence here, but ~halfway between the AAUAAA & U- rich sequences Repeating sequence Conserved sequences/regions in a mammalian pre-mRNA that are involved in termination and polyadenylation
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POLYADENYLATION MACHINERY CPSF: cleavage/polyadenylation specificity factor CstF: cleavage stimulation factor CF: cleavage factor PAP: poly(A) polymerase PC4: regulates termination Ssu72: facilitates cleavage
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Factors involved in cleavage and poly(A) addition are carried to the poly(A) site by the RNAPII complex
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Topic 29, termination of transcription, RNAi.ppt.edu -...

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