{{Short description|"Ribonucleases", "Gene silencing", "non-coding RNAs", "Plant proteins", "Protein stubs"}} {{Infobox nonhuman protein | Name = Endoribonuclease Dicer homolog 3 | Symbol = DCL3 | UniProt = Q9LXW7 | Organism = Arabidopsis thaliana | image = 7VG2_Dcl3-Tas1a40nt.gif | caption = Cartoon representation of Arabidopsis DCL3 (red) in complex with 41nt TAS1a reverse strand (blue), based on atomic coordinates of PDB 7VG2 (Wang Q. et al 2021), rendered with open software Mol Star. | AltSymbols = AT3G43920 }}
'''DCL3''' (Dicer-like 3) is a plant gene that encodes a ribonuclease III enzyme involved in the RNA-directed DNA methylation (RdDM) pathway, a plant-specific mechanism of transcriptional gene silencing.<ref name="Law2010">{{cite journal | vauthors = Law JA, Jacobsen SE | title = Establishing, maintaining and modifying DNA methylation patterns in plants and animals | journal = Nature Reviews Genetics | volume = 11 | issue = 3 | pages = 204–220 | date = 2010 | doi = 10.1038/nrg2719 | pmid = 20142834 }}</ref><ref name="Matzke2014">{{cite journal | vauthors = Matzke MA, Mosher RA | title = RNA-directed DNA methylation: an epigenetic pathway of increasing complexity | journal = Nature Reviews Genetics | volume = 15 | issue = 6 | pages = 394–408 | date = 2014 | doi = 10.1038/nrg3683 | pmid = 24805120 }}</ref> DCL3 processes double-stranded RNA (dsRNA) precursors into 24-nucleotide small interfering RNAs (siRNAs) that guide epigenetic modification of target genomic loci.<ref name="Law2010" />
DCL3 is one of several Dicer-like (DCL) proteins encoded in plant genomes. Unlike DCL1, which primarily generates microRNAs, and DCL4, which produces 21-nucleotide siRNAs, DCL3 is specialized for the biogenesis of 24-nucleotide siRNAs that function in heterochromatic silencing and transposon repression.<ref name="Matzke2014" />
== Function ==
In plants, the RNA-directed DNA methylation (RdDM) pathway mediates transcriptional silencing of repetitive elements and transposable elements through small RNA–guided epigenetic modification. DCL3 plays a central role in this pathway by generating 24-nucleotide siRNAs from endogenous dsRNA substrates.<ref name="Wang2021">{{cite journal | vauthors = Wang Q, Xue Y, Zhang L, Zhong Z, Feng S, Wang C, Xiao L, Yang Z, Harris CJ, Wu Z, Zhai J, Yang M, Li S, Jacobsen SE, Du J | display-authors = 6 | title = Mechanism of siRNA production by a plant Dicer-RNA complex in dicing-competent conformation | journal = Science | volume = 374 | issue = 6571 | pages = 1152–1157 | date = November 2021 | pmid = 34648373 | pmc = 8682726 | doi = 10.1126/science.abl4546 | bibcode = 2021Sci...374.1152W }}</ref>
These dsRNA precursors are derived primarily from transcripts produced by RNA polymerase IV at heterochromatic loci. The single-stranded RNA products of Pol IV are converted into double-stranded RNA by RNA-dependent RNA polymerase 2 (RDR2). DCL3 then cleaves these dsRNA molecules into 24-nt siRNAs.<ref name="Wang2021" />
The resulting siRNAs are incorporated into the Argonaute 4 (AGO4) protein. AGO4-associated siRNAs base-pair with scaffold transcripts generated by RNA polymerase V, facilitating recruitment of domains-rearranged methylase 2 (DRM2). This process results in cytosine DNA methylation and transcriptional repression of the target locus.<ref name="Wang2021" />
== Evolutionary history == DCL3 arose as a specialized paralog within the plant Dicer-like (DCL) gene family during early land plant evolution.<ref name="Law2010" /><ref name="Matzke2014" /><ref name="Huang2015">{{cite journal | vauthors = Huang Y, Kendall T, Forsythe ES, Dorantes-Acosta A, Li S, Caballero-Pérez J, Chen X, Arteaga-Vázquez M, Beilstein MA, Mosher RA | display-authors = 6 | title = Ancient Origin and Recent Innovations of RNA Polymerase IV and V | journal = Molecular Biology and Evolution | volume = 32 | issue = 7 | pages = 1788–1799 | date = 2015 | doi = 10.1093/molbev/msv060 | pmid = 25767205 | pmc = 4476159 }}</ref> Phylogenetic analyses indicate that DCL3 is present in bryophytes and vascular plants, consistent with the early establishment of RNA-directed DNA methylation (RdDM) pathways in terrestrial plant lineages.<ref name="Matzke2014" /><ref name="Huang2015" /> In contrast to animal Dicer proteins, which primarily generate microRNAs and siRNAs involved in post-transcriptional regulation, plant DCL3 became functionally specialized for the production of 24-nucleotide siRNAs associated with transcriptional gene silencing and heterochromatin formation.<ref name="Law2010" />
The emergence of DCL3 coincided with the evolution of plant-specific RNA polymerases, including RNA polymerase IV and RNA polymerase V, which are central to the RdDM pathway.<ref name="Huang2015" /> This coordinated expansion of silencing machinery enabled plants to establish robust epigenetic regulation of transposable elements and repetitive DNA. Comparative genomic studies suggest that the 24-nucleotide siRNA pathway is broadly conserved across land plants, reflecting an early and stable integration of DCL3-mediated silencing into plant genome defense and epigenetic regulation systems.<ref name="Law2010" />
== References == {{reflist}}
Category:Ribonucleases Category:Plant genes Category:Plant proteins Category:RNA interference Category:RNA-binding proteins