Leonaitė Bronislava, Han Zhong, Basquin Jérôme, Bonneau Fabien, Libri Domenico, Porrua Odil, Conti Elena
Max Planck Institute of Biochemistry, Munich, Germany.
Graduate School of Quantitative Biosciences, Ludwig-Maximilians-University, Munich, Germany.
EMBO J. 2017 Jun 1;36(11):1590-1604. doi: 10.15252/embj.201696174. Epub 2017 Apr 13.
The superfamily 1B (SF1B) helicase Sen1 is an essential protein that plays a key role in the termination of non-coding transcription in yeast. Here, we identified the ~90 kDa helicase core of Sen1 as sufficient for transcription termination and determined the corresponding structure at 1.8 Å resolution. In addition to the catalytic and auxiliary subdomains characteristic of the SF1B family, Sen1 has a distinct and evolutionarily conserved structural feature that "braces" the helicase core. Comparative structural analyses indicate that the "brace" is essential in shaping a favorable conformation for RNA binding and unwinding. We also show that subdomain 1C (the "prong") is an essential element for 5'-3' unwinding and for Sen1-mediated transcription termination Finally, yeast Sen1 mutant proteins mimicking the disease forms of the human orthologue, senataxin, show lower capacity of RNA unwinding and impairment of transcription termination The combined biochemical and structural data thus provide a molecular model for the specificity of Sen1 in transcription termination and more generally for the unwinding mechanism of 5'-3' helicases.
超家族1B（SF1B）解旋酶Sen1是一种必需蛋白，在酵母非编码转录的终止过程中起关键作用。在此，我们确定Sen1约90 kDa的解旋酶核心足以实现转录终止，并以1.8 Å的分辨率确定了相应结构。除了SF1B家族特有的催化和辅助亚结构域外，Sen1还有一个独特且在进化上保守的结构特征，它“支撑”着解旋酶核心。比较结构分析表明，该“支撑”结构对于形成有利于RNA结合和解旋的构象至关重要。我们还表明，亚结构域1C（“叉”）是5'-3'解旋以及Sen1介导的转录终止的必需元件。最后，模拟人类同源物senataxin疾病形式的酵母Sen1突变蛋白表现出较低的RNA解旋能力和转录终止缺陷。因此，综合的生化和结构数据为Sen1在转录终止中的特异性以及更普遍的5'-3'解旋酶的解旋机制提供了分子模型。
