Aviv Tzvi, Lin Zhen, Ben-Ari Giora, Smibert Craig A, Sicheri Frank
Program in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario, M5G 1X5, Canada.
Nat Struct Mol Biol. 2006 Feb;13(2):168-76. doi: 10.1038/nsmb1053. Epub 2006 Jan 22.
The SAM domain of the Saccharomyces cerevisiae post-transcriptional regulator Vts1p epitomizes a subfamily of SAM domains conserved from yeast to humans that function as sequence-specific RNA-binding domains. Here we report the 2.0-A X-ray structure of the Vts1p SAM domain bound to a high-affinity RNA ligand. Specificity of RNA binding arises from the association of a guanosine loop base with a shallow pocket on the SAM domain and from multiple SAM domain contacts to the unique backbone structure of the loop, defined in part by a nonplanar base pair within the loop. We have validated NNF1 as an endogenous target of Vts1p among 79 transcripts that copurify with Vts1p. Bioinformatic analysis of these mRNAs demonstrates that the RNA-binding specificity of Vts1p in vivo is probably more stringent than that of the isolated SAM domain in vitro.
酿酒酵母转录后调节因子Vts1p的SAM结构域是从酵母到人类保守的SAM结构域亚家族的代表，其作为序列特异性RNA结合结构域发挥作用。在此，我们报告了与高亲和力RNA配体结合的Vts1p SAM结构域的2.0埃X射线结构。RNA结合的特异性源于鸟苷环碱基与SAM结构域上一个浅口袋的结合，以及SAM结构域与环独特主链结构的多个接触，环的独特主链结构部分由环内的一个非平面碱基对定义。我们已将NNF1验证为在与Vts1p共纯化的79个转录本中Vts1p的一个内源性靶点。对这些mRNA的生物信息学分析表明，Vts1p在体内的RNA结合特异性可能比体外分离的SAM结构域更严格。
