TY - JOUR TI - A crystal structure of a collaborative RNA regulatory complex reveals mechanisms to refine target specificity AU - Qiu, Chen AU - Bhat, Vandita D AU - Rajeev, Sanjana AU - Zhang, Chi AU - Lasley, Alexa E AU - Wine, Robert N AU - Campbell, Zachary T AU - Hall, Traci M Tanaka A2 - Nilsen, Timothy W A2 - Manley, James L VL - 8 PY - 2019 DA - 2019/08/09 SP - e48968 C1 - eLife 2019;8:e48968 DO - 10.7554/eLife.48968 UR - https://doi.org/10.7554/eLife.48968 AB - In the Caenorhabditis elegans germline, fem-3 Binding Factor (FBF) partners with LST-1 to maintain stem cells. A crystal structure of an FBF-2/LST-1/RNA complex revealed that FBF-2 recognizes a short RNA motif different from the characteristic 9-nt FBF binding element, and compact motif recognition coincided with curvature changes in the FBF-2 scaffold. Previously, we engineered FBF-2 to favor recognition of shorter RNA motifs without curvature change (Bhat et al., 2019). In vitro selection of RNAs bound by FBF-2 suggested sequence specificity in the central region of the compact element. This bias, reflected in the crystal structure, was validated in RNA-binding assays. FBF-2 has the intrinsic ability to bind to this shorter motif. LST-1 weakens FBF-2 binding affinity for short and long motifs, which may increase target selectivity. Our findings highlight the role of FBF scaffold flexibility in RNA recognition and suggest a new mechanism by which protein partners refine target site selection. KW - PUF protein KW - RNA-binding protein KW - RNA KW - X-ray crystallography JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -