Figure 2.

ATPase mediated nuclear mRNP assembly. (A) Yeast TREX complex THO•Sub2•Yra1 travels with RNA Pol II and facilitates loading of the export receptor onto mRNA. (B) A detailed view of the stepwise remodeling reactions driven by the Sub2 ATPase. THO is omitted from the RNA because the dynamics of THO association with mRNA is not known. (C) A 6.0 Å resolution structure of Sub2 bound to a THO core complex which contains S. cerevisiae Tho2_1–1207, Hpr1_1–603, Mft1_1–256, and Thp2_1–26, as well as S. bayanus Tex1_1–380 (PDB ID 5SUQ). Top two panels show the overall architecture of the complex. THO is represented by a polyalanine model and only the Tex1 subunit is assigned. The bottom panel highlights the THO-Sub2 binding interface. (D) Structure of Sub2 in association with a truncated Yra1 (Yra1-C, a.a. 208–226) and poly (U) RNA in the presence of ADP•BeF₃ (PDB ID 5SUP). The bound RNA is sharply bent, which is characteristic of DEAD-box proteins. The Yra1 region preceding the crystallized fragment is capable of binding RNA (depicted by a green dashed line), and has been proposed to extend the RNA binding site in the Sub2•Yra1 complex.