The Role of Caenorhabditis elegans dicer in endogenous small RNA silencing pathways

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Title The Role of Caenorhabditis elegans dicer in endogenous small RNA silencing pathways
Publication Type dissertation
School or College School of Medicine
Department Biochemistry
Author Welker, Noah Christopher
Date 2010-02-17
Description RNA interference (RNAi) was originally identified as a conserved biological response to exogenous double-stranded RNA (dsRNA). During this response, dsRNA is processed into 21-23 nucleotide small interfering RNAs (siRNAs) by the ribonuclease III enzyme Dicer. siRNAs produced by this pathway initiate the sequence specific degradation of their cognate messenger RNAs (mRNAs). While RNAi was originally discovered as a response to exogenous dsRNA, during the time of my dissertation research, it has become clear that endogenous dsRNA is responsible for regulating many biological processes. Dicer is also responsible for processing endogenous dsRNA in the form of micro- RNAs (miRNAs) and many endogenous-siRNAs (endo-siRNAs). The effects that Dicer dependent endo-siRNAs and miRNAs have on their cognate mRNAs was unclear prior to the work described in this dissertation. In Chapter 2, I describe my work to characterize how transcripts are misregulated in C. elegans harboring a mutation in the dcr-1 gene. I found that Dicer is responsible for regulating a large number of transcripts including known and predicted miRNA targets. Among the misregulated transcripts in dcr-1 (-/-) was an enrichment for genes involved in C. elegans innate immunity. This later finding prompted me to investigate the role of Dicer's helicase domain, particularly in light of this domain's similarity to RIG-I and MDA-5, two mammalian helicases involved in innate immunity. In Chapter 3,1 describe experiments in which I reintroduced the dcr-1 gene with targeted mutations in the helicase domain into dcr-1 (-/-) C. elegans. Reintroduction of either wild-type (WT) or helicase mutant dcr-1 rescued the fertility defects exhibited in dcr-1 (-/-) animals. Furthermore, I show that dcr-1 helicase mutants have a normal RNAi response following feeding of exogenous dsRNA. I present deep sequencing data that indicates that while dcr-1 helicase mutants process miRNAs to WT levels, they are defective for the production some, but not all, endo-siRNAs. In light of these data, I present a model for Dicer cleavage in which Dicer acts as a processive translocase to process long dsRNA to siRNAs. In Chapter 4, I propose experiments to test this model in light of current literature.
Type Text
Publisher University of Utah
Subject Small Interfering RNA; Caenorhabditis elegans
Subject MESH RNA, Small Interfering; Caenorhabditis elegans
Dissertation Institution University of Utah
Dissertation Name PhD
Language eng
Relation is Version of Digital reproduction of "The role of caenorhabditis elegans dicer in endogenous small rna silencing pathways." Spencer S. Eccles Health Sciences Library. Print version of "The role of caenorhabditis elegans dicer in endogenous small rna silencing pathways.: available at J. Willard Marriott Library Special Collection. QL3.5 2009.W45.
Rights Management © Noah Christopher Welker
Format application/pdf
Format Medium application/pdf
Format Extent 1,455,372 bytes
Source Original: University of Utah Spencer S. Eccles Health Sciences Library
Conversion Specifications Original scanned on Fujitsu fi-5220G as 400 dpi to pdf using ABBYY FineReader 10
ARK ark:/87278/s6gh9zhr
Setname ir_etd
ID 192769
Reference URL https://collections.lib.utah.edu/ark:/87278/s6gh9zhr
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