Specificity of ARGONAUTE7-miR390 interaction and dual functionality in

Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331, USA.
Cell (Impact Factor: 32.24). 05/2008; 133(1):128-41. DOI: 10.1016/j.cell.2008.02.033
Source: PubMed


Trans-acting siRNA form through a refined RNAi mechanism in plants. miRNA-guided cleavage triggers entry of precursor transcripts into an RNA-DEPENDENT RNA POLYMERASE6 pathway, and sets the register for phased tasiRNA formation by DICER-LIKE4. Here, we show that miR390-ARGONAUTE7 complexes function in distinct cleavage or noncleavage modes at two target sites in TAS3a transcripts. The AGO7 cleavage, but not the noncleavage, function could be provided by AGO1, the dominant miRNA-associated AGO, but only when AGO1 was guided to a modified target site through an alternate miRNA. AGO7 was highly selective for interaction with miR390, and miR390 in turn was excluded from association with AGO1 due entirely to an incompatible 5' adenosine. Analysis of AGO1, AGO2, and AGO7 revealed a potent 5' nucleotide discrimination function for some, although not all, ARGONAUTEs. miR390 and AGO7, therefore, evolved as a highly specific miRNA guide/effector protein pair to function at two distinct tasiRNA biogenesis steps.

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    • "This evidence has been provided recently (Minoia et al., 2014). In leaves of PSTVd-infected N. benthamiana , the endogenous AGO1 and distinct epitope-tagged AGOs from A. thaliana that were overexpressed —AGO1, AGO2, AGO3, AGO4, AGO5 and AGO9, but not AGO6, AGO7 and AGO10—associate with vd-sRNAs displaying the same properties (5 -terminal nucleotide and size) reported previously for endogenous and viral sRNAs (Mi et al., 2008; Montgomery et al., 2008; Takeda et al., 2008). The AGO-loaded vd-sRNAs adopt specific distributions along the viroid genome. "
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    • "The double stranded intermediate is then processed by DICER-LIKE 4 (DCL4) and DEDICATED dsRNA-BINDING PROTEIN 4 (DRB4) to phased 21nt tasiRNAs which are incorporated into AGO-containing complexes to target complementary sequences (Vazquez et al. 2004; Allen et al. 2005; Gasciolli et al. 2005; Xie et al. 2005b; Yoshikawa et al. 2005; Adenot et al. 2006). AGO1 (Peragine et al. 2004; Vazquez et al. 2004; Allen et al. 2005; Yoshikawa et al. 2005) and AGO7 (Adenot et al. 2006; Fahlgren et al. 2006; Montgomery et al. 2008) proteins have been found to be involved in tasiRNA function. The miRNA cleavage site determines the phase and is critical for the production of specific tasiRNAs (Allen et al. 2005). "
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    • " - nt phasiRNAs . However , the pro - portion of 3 0 ' U ' ends is significantly higher for 22 - nt than for 21 - nt phasiRNAs . Knowing that data from Arabidopsis show that 5 0 ' U ' small RNAs are enriched in AGO1 ( Mi et al . , 2008 ) , while 5 0 ' A ' 21 - to 22 - nt small RNAs are enriched in AGO2 , AGO4 , AGO6 , or AGO9 ( Mi et al . , 2008 ; Montgomery et al . , 2008 ; Havecker et al . , 2010 ; McCue et al . , 2015 ) , it is likely that the differentially abundant pha - siRNAs may be sorted to AGOs based on their 5 0 sequences . The function of the 3 0 variation in the 22 - nt phasiRNAs remains to be determined , but could result from 3 0 tailing mediated by HESO1 or related nucleotidyl transferases"
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