Recent studies on enzymes regulating dynamic N6-methyl-adenosine （m6A） in RNA together with the findings from m6A-methylated RNA immunoprecipitation followed by high-throughput sequencing （MeRIP-seq/m6A- seq） have...Recent studies on enzymes regulating dynamic N6-methyl-adenosine （m6A） in RNA together with the findings from m6A-methylated RNA immunoprecipitation followed by high-throughput sequencing （MeRIP-seq/m6A- seq） have revealed a broad biological role of m6A in RNA processing, development, differentiation, metabolism and fertility. RNA m6A methylation is catalyzed by a multi- component methyltransferase complex composed of at least three subunits： METTL3, METTL14 and Wilms tumor 1-associated protein （WTAP）, in which METTL3 and METTL14 serve as catalytic subunits, while WTAP as reg- ulatory subunit. Dioxygenases FTO and ALKBH5, as the first two known m6A demethylases, catalyze m6A removal. Five m6A-binding proteins are classified into cytoplasmic YT521-B homology （YTH） domain-containing family YT- HDF1-3 and nuclear YTHDC1-2. Perturbation of enzy- matic activities catalyzing dynamic m6A results in altered expression of thousands of genes and affects mRNA stability and splicing at the cellular level. Here, we summarize recent discoveries about m6A methyltransferases （writers）,demethylases （erasers） and binding proteins （readers）, and further discuss the potential impacts of m6A on RNA pro- cessing, especially on mRNA splicing.展开更多
The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by in...The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide. The calculations show that dioxygen attack on the copper complex is energetically favorable. The adduct has a possible near-degeneracy of states between [Cu2＋-（substrate H＋）] and [Cu＋-（sub- strate-H）. ], and in addition the pyramidalized C2 atom is ideally suited for forming a dioxygembridged structure. In the next step, the C3-C4 bond is cleaved and intermediate lnt5 is formed via transition state TS4. Finally, the Oa-Ob and C2-C3 bonds are cleaved, and CO is released in one concerted transition state （TS5） with the barrier of 63.25 and 61.91 k J/tool in the gas phase and protein environments, respectively. On the basis of our proposed reaction mechanism, this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol. Our work provides some valuable fundamental insights into the behavior of this enzyme.展开更多
基金supported by the National BasicResearch Program of China(2011CB510103,2014CB964902)the National Science Foundation of China(91319308,31430022 and31400672)Strategic Priority Research Program of Chinese Academy ofSciences(XDB14030300)
文摘Recent studies on enzymes regulating dynamic N6-methyl-adenosine （m6A） in RNA together with the findings from m6A-methylated RNA immunoprecipitation followed by high-throughput sequencing （MeRIP-seq/m6A- seq） have revealed a broad biological role of m6A in RNA processing, development, differentiation, metabolism and fertility. RNA m6A methylation is catalyzed by a multi- component methyltransferase complex composed of at least three subunits： METTL3, METTL14 and Wilms tumor 1-associated protein （WTAP）, in which METTL3 and METTL14 serve as catalytic subunits, while WTAP as reg- ulatory subunit. Dioxygenases FTO and ALKBH5, as the first two known m6A demethylases, catalyze m6A removal. Five m6A-binding proteins are classified into cytoplasmic YT521-B homology （YTH） domain-containing family YT- HDF1-3 and nuclear YTHDC1-2. Perturbation of enzy- matic activities catalyzing dynamic m6A results in altered expression of thousands of genes and affects mRNA stability and splicing at the cellular level. Here, we summarize recent discoveries about m6A methyltransferases （writers）,demethylases （erasers） and binding proteins （readers）, and further discuss the potential impacts of m6A on RNA pro- cessing, especially on mRNA splicing.
基金supported by the National Natural Science Foundation of China (21073164,20673098)the Natural Science Foundation of Zhejiang Province (Y4100620)the Research Foundation of the Education Bureau of Zhejiang Province (Y200906517)
文摘The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide. The calculations show that dioxygen attack on the copper complex is energetically favorable. The adduct has a possible near-degeneracy of states between [Cu2＋-（substrate H＋）] and [Cu＋-（sub- strate-H）. ], and in addition the pyramidalized C2 atom is ideally suited for forming a dioxygembridged structure. In the next step, the C3-C4 bond is cleaved and intermediate lnt5 is formed via transition state TS4. Finally, the Oa-Ob and C2-C3 bonds are cleaved, and CO is released in one concerted transition state （TS5） with the barrier of 63.25 and 61.91 k J/tool in the gas phase and protein environments, respectively. On the basis of our proposed reaction mechanism, this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol. Our work provides some valuable fundamental insights into the behavior of this enzyme.
