2n3h | pdb_00002n3h
Solution structure of DRB4 dsRBD2 (viz. DRB4(81-151))
Structural highlights
FunctionDRB4_ARATH Double-stranded RNA-binding protein involved in RNA-mediated post-transcriptional gene silencing (PTGS). Functions in the trans-acting small interfering RNAs (ta-siRNAs) biogenesis by binding and assisting DICER-LIKE 4 (DCL4). Required for DCL4 activity. Required for the 21 nucleotide ta-siRNAs production of the TAS3 transcript in leaves but not in flowers. Plays an important role in silencing RNA of both DNA and RNA viruses. Involved with argonaute 7 (AGO7) and RDR6 in turnip crinkle virus (TCV) silencing. May not be directly involved in viral siRNA production. May stabilize the 21 nucleotide viral siRNAs and deliver them to the RISC complex. Targeted by the viral silencing suppressor (VSR) transactivator/viroplasmin (TAV) protein of the cauliflower mosaic virus (CaMV) that inactivates DRB4 function in RNA silencing. Probably not involved in the guide strand selection from RNA duplexes. Involved in leaf morphology through its function in ta-siRNA-mediated silencing.[1] [2] [3] [4] Publication Abstract from PubMedIn Arabidopsis thaliana, endogenous trans-acting and exogenous siRNA pathways are initiated by the interaction of DRB4 with trigger dsRNA. Further, DCL4:DRB4 complex cleaves the dsRNA into 21 bp siRNA. Understanding molecular determinants and mechanistic details of dsRNA recognition by DRB4 is vital for inducing long-term RNAi-mediated gene regulation in plants. Here, we present solution structures of individual and concatenated DRB4 dsRBDs and demonstrate modes of dsRNA binding by employing NMR, ITC and site-specific mutagenesis. While both dsRBDs adopt the canonical alpha-beta-beta-beta-alpha fold, key structural differences and ms-mus dynamics located at the RNA binding region were observed for dsRBD1. These features favor dsRBD1 to orient itself and make stronger tripartite contact with dsRNA, a feature missing in dsRBD2. Additionally, the inter-domain orientation induced by the linker restricts the mobility of dsRBD2, resulting in the steric hindrance of alpha1 helix in dsRBD2, and leads in further reduction of its dsRNA binding activity. Our study deciphers functional roles of DRB4 domains by showing that dsRBD1 drives the tasiRNA/siRNA pathway. Furthermore, we identify a potential role of the C-terminal region of DRB4 in protein:protein interaction as it possesses six PxxP motifs, binds to Zn2+ and contains a small structural domain. DRB4 dsRBD1 drives dsRNA recognition in Arabidopsis thaliana tasi/siRNA pathway.,Chiliveri SC, Aute R, Rai U, Deshmukh MV Nucleic Acids Res. 2017 Aug 21;45(14):8551-8563. doi: 10.1093/nar/gkx481. PMID:28575480[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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