Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States.
Department of Microbiology and Molecular Genetics, University of Texas Health Science Center at Houston, Houston, Texas 77030, United States.
Biochemistry. 2024 Jan 2;63(1):159-170. doi: 10.1021/acs.biochem.3c00401. Epub 2023 Dec 12.
Mtr4 is an essential RNA helicase involved in nuclear RNA processing and degradation and is a member of the Ski2-like helicase family. Ski2-like helicases share a common core architecture that includes two RecA-like domains, a winged helix, and a helical bundle (HB) domain. In Mtr4, a short C-terminal tail immediately follows the HB domain and is positioned at the interface of the RecA-like domains. The tail ends with a SLYΦ sequence motif that is highly conserved in a subset of Ski2-like helicases. Here, we show that this sequence is critical for Mtr4 function. Mutations in the C-terminus result in decreased RNA unwinding activity. Mtr4 is a key activator of the RNA exosome complex, and mutations in the SLYΦ motif produce a slow growth phenotype when combined with a partial exosome defect in , suggesting an important role of the C-terminus of Mtr4 and the RNA exosome. We further demonstrate that C-terminal mutations impair RNA degradation activity by the major RNA exosome nuclease Rrp44 . These data demonstrate a role for the Mtr4 C-terminus in regulating helicase activity and coordinating Mtr4-exosome interactions.
Mtr4 是一种必需的 RNA 解旋酶，参与核 RNA 加工和降解，是 Ski2 样解旋酶家族的成员。Ski2 样解旋酶具有共同的核心结构，包括两个 RecA 样结构域、一个翼状螺旋和一个螺旋束 (HB) 结构域。在 Mtr4 中，HB 结构域之后紧接着是一个短的 C 端尾巴，位于 RecA 样结构域的界面处。尾巴以 SLYΦ 序列基序结尾，该基序在一组 Ski2 样解旋酶中高度保守。在这里，我们表明该序列对于 Mtr4 功能至关重要。C 端突变导致 RNA 解链活性降低。Mtr4 是 RNA 外切体复合物的关键激活剂，当与 中的部分外切体缺陷结合时，SLYΦ 基序中的突变会产生生长缓慢的表型，这表明 Mtr4 的 C 端和 RNA 外切体具有重要作用。我们进一步证明 C 端突变会损害主要的 RNA 外切体核酶 Rrp44 的 RNA 降解活性。这些数据表明 Mtr4 C 端在调节解旋酶活性和协调 Mtr4-外切体相互作用方面发挥作用。
