MCB 121 Lecture 18

MCB 121 Lecture 18 - MCB 121 Lecture 18 RNAi I. overview of...

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Unformatted text preview: MCB 121 Lecture 18 RNAi I. overview of mechanism II. Types A. SiRNA = post-transcriptional silencing B. miRNA = post-transcriptional silencing C. RNA-induced transcriptional silencing ------------------------------------------------------------------- SiRNA (small interfering RNA) = silence the exogenous RNA sequence that comes into the cell (such as RNA viruses) or keeping the transcription of repeated elements decreased. miRNA (microRNA) = RNA encoding in the genome that performs function in gene regulation RNAi can extend to chromosome level by bring the modifying proteins. I. overview of mechanism:- dsRNA is processed by dicer in the cytoplasm Dicer has two domains- PAZ domain: binds to dsRNA- RNAase III domain: sequence that's homologous to RNase III in Ecoli - products of dicer are short dsRNA (refers to siRNA ), about 21-22bp- Argonaute: complex that brings one strand of siRNA product (which is guide RNA ) = unwinding event involves the transfer of one strand of the siRNA products to Argonaute- guide RNA carried by Argonaute find the target transcript = the guide RNA would base pair with complementary sequence of the target transcript mRNA- this would result gene specific reduction in expression = might involve: 1) RNA cleavage 2) Block translation 3) modify chromatin into heterochromatin <= 1 & 2 occur in cytoplasm, 3 occur in nucleus = the kind of modifications that silencing the gene: a. histone methylation b. histone deacetylation c. DNA (cytosine) methylation - siRNA associates with RNA cleavage and associates with Argonaute which has the slicer activity (AGO-slicer)- miRNA blocks translation - modifying chromatin is carried out by RITS complex -------------------------------------------------------------------------------- SiRNA: Discovery: 1. C.elegans: injection of dsRNA to create gene knock-down - can be used in other cell type to make genetic knock-down gene- introduce the gene which expresses small hairpin structure by using viral vector or transient expression....
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MCB 121 Lecture 18 - MCB 121 Lecture 18 RNAi I. overview of...

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