title: RDR6-mediated synthesis of complementary RNA is terminated by miRNA stably bound to template RNA.
abstract: RNA-dependent RNA polymerase RDR6 is involved in the biogenesis of plant trans-acting siRNAs. This process is initiated by miRNA-directed and Argonaute (AGO) protein-mediated cleavage of TAS gene transcripts. One of the cleavage products is converted by RDR6 to double-stranded (ds)RNA, the substrate for Dicer-like 4 (DCL4). Interestingly, TAS3 transcript contains two target sites for miR390::AGO7 complexes, 5'-non-cleavable and 3'-cleavable. Here we show that RDR6-mediated synthesis of complementary RNA starts at a third nucleotide of the cleaved TAS3 transcript and is terminated by the miR390::AGO7 complex stably bound to the non-cleavable site. Thus, the resulting dsRNA has a short, 2-nt, 3'-overhang and a long, 220-nt, 5'-overhang of the template strand. The short, but not long, overhang is optimal for DCL4 binding, which ensures dsRNA processing from one end into phased siRNA duplexes with 2-nt 3'-overhangs.
authors.affiliation: Institute of Botany, University of Basel, Schönbeinstrasse 6, 4056 Basel, Switzerland.
authors.forename: Rajendran
authors.initials: R
authors.lastname: Rajeswaran
authors.forename: Mikhail M
authors.initials: MM
authors.lastname: Pooggin
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D018075:RNA, Complementary / Q000096:biosynthesis* / Q000737:chemistry; D012330:RNA, Double-Stranded / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D017423:Sequence Analysis, RNA; D013698:Templates, Genetic
chemical_list: D029681:Arabidopsis Proteins; D035683:MicroRNAs; D018075:RNA, Complementary; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; C514575:RDR6 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase