|Structure of the Nab2-N:Gfd1 interface, shown in two views rotated 90° about the vertical axis; Nab2-N is in blue, and Gfd1 is in yellow.
During mRNA biogenesis, immature mRNA needs to be processed, packaged into ribonucleoprotein particles and transported out of the nucleus so translation can commence. This multistep trafficking involves the coordinated efforts of numerous nuclear and cytoplasmic proteins, such as Nab2, which binds to the mRNA poly-A tail and assists in the export and cytoplasmic disassembly of mRNPs. Nab2 interacts with a protein factor called Gfd1 at its N terminus, though not much is known about this interaction because Gfd1is nonessential, and deletion mutants do not alter mRNA export. However, in this study, the authors employed both crystallography and solution NMR to identify the molecular nature of the Nab2-Gfd1 interaction and exploit that information then to design specific mutations for use in genetic and cell biological assays. They found that a Gfd1 mutant defective in Nab2 binding could not rescue the temperature-sensitive growth defects and poly-A accumulation seen in yeast cells lacking the helicase Dbp5 (a key component of the mRNP disassembly machinery), whereas wild-type Gfd1 could. These findings suggest Gfd1acts to facilitate the release of Nab2 from mRNPs in the cytoplasm, providing some detail into a poorly understood aspect of the gene expression pathway.
Structural Basis for the Function of the Sacchromyces cerevisiae Gfd1 Protein in mRNA Nuclear Export
Chao Zheng, Milo B. Fasken, Neil J. Marshall, Christoph Brockmann, Max E. Rubinson, Susan R. Wente, Anita H. Corbett and Murray Stewart
J. Biol. Chem. published online May 12, 2010
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