Structural basis for RNA-silencing suppression by Tomato aspermy virus protein 2b.
The 2b proteins encoded by cucumovirus act as post-transcriptional gene silencing suppressors to counter host defence during infection. Here we report the crystal structure of Tomato aspermy virus 2b (TAV2b) protein bound to a 19 bp small interfering RNA (siRNA) duplex. TAV2b adopts an all alpha-helix structure and forms a homodimer to measure siRNA duplex in a length-preference mode. TAV2b has a pair of hook-like structures to recognize simultaneously two alpha-helical turns of A-form RNA duplex by fitting its alpha-helix backbone into two adjacent major grooves of siRNA duplex. The conserved pi-stackings between tryptophan and the 5'-terminal base of siRNA duplex from both ends enhance the recognition. TAV2b further oligomerizes to form a dimer of dimers through the conserved leucine-zipper-like motif at its amino-terminal alpha-helix. Biochemical experiments suggest that TAV2b might interfere with the post-transcriptional gene silencing pathway by directly binding to siRNA duplex.
Chen
Hong-Ying
HY
Host-Pathogen Interaction Group, National University of Singapore, Singapore.
Yang
Jing
J
Lin
Chengqi
C
Yuan
Y Adam
YA
D000595:Amino Acid Sequence; D002151:Calorimetry; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D017799:Cucumovirus / Q000235:genetics / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000821:virology*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D014764:Viral Proteins