The lin-14 gene is a target of the lin-4 microRNA. When lin-4 is expressed in C.
ID: 94558 • Letter: T
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The lin-14 gene is a target of the lin-4 microRNA. When lin-4 is expressed in C. elegans, lin-14 protein levels are dramatically reduced. You have specific inhibitors that block Drosha, Dicer and the RISC complex (a different inhibitor for each). If you treat late L1 stage worms (a developmental stage characterized by high levels of lin-4 expression) with each of the inhibitors, how would lin-14 protein levels be affected? Would your results be different if you also treated the worms with lin-4 pre-miRNA? In your answer, explain what each enzyme or complex normally does, why the inhibitor would have the effect that it does, and how the presence of lin-4 pre-miRNA would, or would not, change that. The lin-14 gene is a target of the lin-4 microRNA. When lin-4 is expressed in C. elegans, lin-14 protein levels are dramatically reduced. You have specific inhibitors that block Drosha, Dicer and the RISC complex (a different inhibitor for each). If you treat late L1 stage worms (a developmental stage characterized by high levels of lin-4 expression) with each of the inhibitors, how would lin-14 protein levels be affected? Would your results be different if you also treated the worms with lin-4 pre-miRNA? In your answer, explain what each enzyme or complex normally does, why the inhibitor would have the effect that it does, and how the presence of lin-4 pre-miRNA would, or would not, change that.Explanation / Answer
lin-4 is transcribed from autonomous miRNA promoters and is developmentally regulated, with lin-4 miRNA accumulation occurring at the L2 stage of post-embryonic development. Additional to this is the up-regulation of endogenous lin-4 primary transcripts upon appearance of the lin-4 mature form.[4] lin-4 is found on chromosome II in C. elegans and is complementary to sequences in the 3' untranslated region (UTR) of lin-14 mRNA, this complementary transcript containing seven binding sites along with the 9 nucleotide core element CUCAGGGAA. The lin-4:lin-14 duplex is seen to take up an unusual kinked structure, caused by induced changes in the groove dimension and base stacking due to the mismatched base pairs.
MicroRNAs are small, highly conserved non-coding RNA molecules involved in the regulation of gene expression. MicroRNAs are transcribed by RNA polymerases II and III, generating precursors that undergo a series of cleavage events to form mature microRNA. The regulatory functions of microRNAs are accomplished through the RNA-induced silencing complex (RISC). MicroRNA assembles into RISC, activating the complex to target messenger RNA (mRNA) specified by the microRNA.
Human miRNA biogenesis is a two-step process, with both nuclear and subsequent cytoplasmic cleavage events performed by two ribonuclease III endonucleases, Drosha and Dicer The miRNA gene is transcribed to produce a primary miRNA (pri-miRNA) that is processed into a precursor miRNA (pre-miRNA) and subsequently miRNA duplex which ultimately releases mature miRNA ]. MiRNA origin and size appear to determine what nuclear pathway the miRNA will proceed through.
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