User:AimerD/DCL2

DCL2 (an abbreviation of Dicer-like 2) is a gene in plants that codes for the DCL2 protein, a ribonuclease III enzyme involved in processing exogenous double-stranded RNA (dsRNA) into 22 nucleotide small interference RNAs (siRNAs) in Plants. Diverse source of dsRNAs have been characterized, mainly exogenous derived, for instance during the viral infection of double-stranded RNA viruses, where the cleavage of dsRNA produce small RNA products called viral siRNAs or vsi-RNAs. An additional exogenous source of dsRNAs are the transgenic insertions. DCL2 also process endogenous sources as double-stranded RNAs derived of cis-natural antisense transcripts, generating 22nt short interfering RNA (natsi-RNAs); however, the biological relevance, evolutionary conservation and experimental validation of natsi-RNAs remains controversial.

Molecular fuction
Dicer proteins belongs to the RNaselll-like family, a gene family with highly conserved endonuclease in eukaryotes[3]. In Arabidopsis and most of the land Plants, there are four Dicer-like proteins (DCL): DCL1, DCL2, DCL3, and DCL4. They all contain five domains which are DEXD-helicase, helicase-C, domain of unknown function 283 (DUF283), Piwi/Argonaute/Zwille (PAZ) domain, two tandem RNase III domains, and one or two dsRNA-binding domains (dsRBDs) from the N-terminus to C-terminus. In general, the helicase domain utilizes ATP hydrolysis to facilitate the unwinding of dsRNA. The DUF283 domain have been associated as a protein domain involve in facilitation of RNA-RNA base pairing and RNA-binding. The PAZ and RNase III domains are vital for dsRNA cleavage, the PAZ domain recognizes the terminus of the dsRNA and RNase III domains and cuts one of the strands of dsRNA, and the distance between the PAZ domain and RNase III domains is determined by the length of the products. The dsRBD domain facilitates dsRNA binding and also serves as a nonclassical nuclear localization signal.

DCL2 small RNA products as a mobile molecular signal
DCL2 plays an essential role in transitive silencing of transgenes by processing secondary siRNAs. This pathway, which requires DCL4 and RDR6, amplifies silencing by using the target RNA as substrate to generate secondary siRNAs, providing an efficient mechanism for long-distance silencing, in a phenomena called Transitivity of RNA silencing. DCL2 may participate as well with DCL3 in the production of 24 nucleotide repeat-associated siRNAs (ra-siRNAs) which derive from heterochromatin and DNA repeats such as transposons.

Role as antiviral protein
Targeted by the viral silencing suppressor (VSR) protein 2b of the cucumber mosaic virus (CMV) that inactivates DCL2 function in RNA silencing.