Structure of saguaro cactus virus 3′ translational enhancer mimics 5′ cap for eIF4E binding

• 成果类型: Article
• 署名作者: Ojha, Manju; Vogt, Jeff; Das, Naba Krishna; Redmond, Emily; Singh, Karndeep; Al Banna, Hasan; Sadat, Tasnia; Koirala, Deepak
• 署名单位: University System of Maryland; University of Maryland Baltimore County; Howard Hughes Medical Institute; University System of Maryland; University of Maryland Baltimore County
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13751
• DOI: 10.1073/pnas.2313677121
• 发表日期: 2024-01-23
• 关键词: initiation-factor 4e; independent translation; dependent translation; synthetic antibodies; RECOGNITION; protein; oligoribonucleotides; factor-4e; features; element

摘要

The genomes of several plant viruses contain RNA structures at their 3 ' ends called cap-independent translation enhancers (CITEs) that bind the host protein factors such as mRNA 5 ' cap-binding protein eIF4E for promoting cap-independent genome translation. However, the structural basis of such 5 ' cap-binding protein recognition by the uncapped RNA remains largely unknown. Here, we have determined the crystal structure of a 3 ' CITE, panicum mosaic virus-like translation enhancer (PTE) from the saguaro cactus virus (SCV), using a Fab crystallization chaperone. The PTE RNA folds into a three-way junction architecture with a pseudoknot between the purine-rich R domain and pyrimidine-rich Y domain, which organizes the overall structure to protrude out a specific guanine nucleotide, G18, from the R domain that comprises a major interaction site for the eIF4E binding. The superimposable crystal structures of the wild-type, G18A, G18C, and G18U mutants suggest that the PTE scaffold is preorganized with the flipped-out G18 ready to dock into the eIF4E 5 ' cap-binding pocket. The binding studies with wheat and human eIF4Es using gel electrophoresis and isothermal titration calorimetry, and molecular docking computation for the PTE-eIF4E complex demonstrated that the PTE structure essentially mimics the mRNA 5 ' cap for eIF4E binding. Such 5 ' cap mimicry by the uncapped and structured viral RNA highlights how viruses can exploit RNA structures to mimic the host protein-binding partners and bypass the canonical mechanisms for their genome translation, providing opportunities for a better understanding of virus-host interactions and non-canonical translation mechanisms found in many pathogenic RNA viruses.