Dicerlike

Dicer-like proteins are a family of ribonuclease III enzymes that process long double-stranded RNA into small regulatory RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs). They are key components of RNA interference and RNA silencing pathways that regulate gene expression and defend against viruses. The typical Dicer-like protein contains an N-terminal helicase/ATPase domain, a PAZ domain that binds RNA ends, two RNase III catalytic domains, and a double-stranded RNA-binding domain, functioning as a dimer to generate small RNA duplexes of defined lengths.

In plants, the Dicer-like (DCL) family is expanded and subdivided (for example, DCL1–DCL4 in many species). DCL1 primarily processes miRNA precursors; DCL4 generates 21-nucleotide siRNAs involved in trans-acting siRNA and antiviral silencing; DCL2 produces 22-nucleotide siRNAs that can act when DCL4 is compromised; DCL3 produces 24-nucleotide siRNAs that direct RNA-directed DNA methylation (RdDM). The specialization of DCL enzymes supports diverse silencing pathways and developmental regulation. In contrast, animals typically rely on a single Dicer enzyme to generate both miRNAs and siRNAs, though some lineages harbor additional Dicer-like variants with distinct functions.

Evolutionarily, Dicer-like genes are conserved across eukaryotes but have diversified through gene duplication and subfunctionalization, particularly in land plants. Their activity is coordinated with partner proteins such as Argonaute and RNA-dependent RNA polymerases to produce, load, and implement small RNAs that guide post-transcriptional regulation and epigenetic modifications.