In Arabidopsis thaliana, it associates with small interfering RNAs that help target RNA-directed DNA methylation. Sequence complementarity supplies specificity while partner proteins connect recognition to a chromatin modification rather than cleavage of every matching transcript. [ref]
ARGONAUTE4 control of locus-specific siRNA accumulation and DNA and histone methylation by Daniel Zilberman and others. 2003, AGO4-dependent methylation and silencing
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