Wang Ping, Doxtader Katelyn A, Nam Yunsun
Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Division of Basic Reproductive Biology Research, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Division of Basic Reproductive Biology Research, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Mol Cell. 2016 Jul 21;63(2):306-317. doi: 10.1016/j.molcel.2016.05.041. Epub 2016 Jun 30.
N(6)-methyladenosine (m(6)A) is a prevalent, reversible chemical modification of functional RNAs and is important for central events in biology. The core m(6)A writers are Mettl3 and Mettl14, which both contain methyltransferase domains. How Mettl3 and Mettl14 cooperate to catalyze methylation of adenosines has remained elusive. We present crystal structures of the complex of Mettl3/Mettl14 methyltransferase domains in apo form as well as with bound S-adenosylmethionine (SAM) or S-adenosylhomocysteine (SAH) in the catalytic site. We determine that the heterodimeric complex of methyltransferase domains, combined with CCCH motifs, constitutes the minimally required regions for creating m(6)A modifications in vitro. We also show that Mettl3 is the catalytically active subunit, while Mettl14 plays a structural role critical for substrate recognition. Our model provides a molecular explanation for why certain mutations of Mettl3 and Mettl14 lead to impaired function of the methyltransferase complex.
N⁶-甲基腺苷（m⁶A）是功能性RNA中一种普遍存在的、可逆的化学修饰，对生物学中的核心事件至关重要。核心m⁶A甲基转移酶是Mettl3和Mettl14，它们都含有甲基转移酶结构域。Mettl3和Mettl14如何协同催化腺苷的甲基化一直不清楚。我们展示了apo形式的Mettl3/Mettl14甲基转移酶结构域复合物以及催化位点结合有S-腺苷甲硫氨酸（SAM）或S-腺苷同型半胱氨酸（SAH）的晶体结构。我们确定甲基转移酶结构域的异二聚体复合物与CCCH基序相结合，构成了体外产生m⁶A修饰所需的最小区域。我们还表明Mettl3是具有催化活性的亚基，而Mettl14在底物识别中起关键的结构作用。我们的模型为Mettl3和Mettl14的某些突变为何会导致甲基转移酶复合物功能受损提供了分子解释。
