Structure and function of DICER. Presentation by Florian Ahrend. Overview. Introduction Function of RNAi Function of Dicer The RNase III – family Structure of Giardia -Dicer Giardia -Dicer vs Human-Dicer Flexibilty of Dicer The Argonaute – family RISC-loading Summary. Introduction.
Presentation by Florian Ahrend
-cleaves 2nt-3´-overhang-dsRNA; endogenous (pre-miRNA) and exogenous dsRNA into miRNA and siRNA
-products interact with RISC for sequence-specific gene-silencing
-Dicer initiates RNAi by processing dsRNA substrates
-it is a molecular ruler, that measures and cleaves dsRNA into small fragments of discrete size (about 21-27 nucleotides in length) by hydrolysis
-Dicer (of higher eukaryotes) aids to load produced short dsRNA into RISC (RNA-induced-silencing-complex)
RNase = Ribonuklease Dicer = specialized RNase
-simplest and smallest RNase III
-consists of: single RNase III-domain +
dsRBD (= dsRNA-Binding-Domain)
-found in bacteria, bacteriophage
and some fungi
-Dicer from Giardia intestinalis is a kind of “minimal dicer”, with only core-functions
-misses Helicase and DUF
-processes dsRNA from helical end in a fashion similar to human Dicer
-looks like a hatchet
Comparing Giardia-Dicer and Aquifex-RNase III
-creates a large positively charged region
-guides the dsRNA
-connection between RNase IIIa and RNase IIIb
Human-Dicer contains some additional domains, like the DUF283 and DExD-Helicase
-about 100 amino acids long
-lies between helicase and PAZ-domain
-in higher eukaryotes: probably platform function
-possible functions include unwinding products, translocating Dicer, fascilitating handoff of products
Three rigid regions of Dicer (RNase-region, platform-region and PAZ-domain) linked by two hinges allows evolutionary flexibility.
-evolutionary highly conserved
-consist of: PIWI-domain and PAZ-domain
RISC-loading-complex needed, which
consist of Argonaute, Dicer and TRBP
Which strand of the dsRNA acts
as guide for gene-silencing?
-Macrae, I.J., et al., Structural basis for double-stranded RNA processing by Dicer. Science, 2006. 311(5758): p. 195-8.
-MacRae, I.J. and J.A. Doudna, Ribonuclease revisited: structural insights into ribonuclease III family enzymes. Curr Opin Struct Biol, 2007. 17(1): p. 138-45.
-Macrae, I.J., et al., Structure of Dicer and mechanistic implications for RNAi. Cold Spring Harb Symp Quant Biol, 2006. 71: p. 73-80.
-Zhang, H., et al., Single processing center models for human Dicer and bacterial RNase III. Cell, 2004. 118(1): p. 57-68.
-Skript zur Vorlesung “Genregulation”, Professor Nellen, Uni Kassel