11BIS1012013MicroRNALect11

Lrodriguez 2013

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Unformatted text preview: wn below are two genes (A and B) transcribed Shown from different strands (mRNA). Primary (pri-miRNA) and miRNA are shown as blue arrows. Notice that the pri- and miRNAs are non-coding (ORF-less) and can be made from either strand either between genes or within introns. It is unlikely that miRNAs inhibit (after dicer processing) the mRNAs of the genes they are made from. Gene A pri-miRNA miRNA mRNA mRNA mRNA miRNA Exons Gene B BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 10 MiRNAs are highly conserved and processed MiRNAs BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 11 11 RNA Interference (RNAi): 5 Points 1. 2. 3. 4. 5. Silence expression of mRNA with siRNA requires the “RNASilence “RNAInduced Silencing Complex”(RISC) and its 3 enzymatic Induced activities“Dicer,” Helicase and “Slicer.” Other enzymes may also be involved (e.g., Drosha, nuclear endoribonuclease). be The endonuclease activity of “Dicer”converts ds-shRNA into 21The “Dicer”converts 25 bp RNA (siRNA) making it competent for interference. The helicase activity of RISC, unwinds the “passenger” strand The of siRNA from the “guide” strand. of The guide strand is bound by Argonaut (Ago2) which facilitates The binding to its complementary target mRNA and the endonuclease activity of RISC (“slicer”) cleaves the mRNA. endonuclease “slicer”) Exoribonucleases degrade the RNA from its ends. Exoribonucleases In plants, the RNA-dependent, RNA polymerase activity of In Dicer synthesizes new siRNA so it can pass from one cell to the next and from one cell division to the next (i.e. infectious). the BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 12 miRNA Processing and Mode of Action Immediately after transcription, pri-miRNAs are enzymatically cropp...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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