激酶结构域插入决定了CLK激酶在SR蛋白磷酸化中的不同作用。
Kinase domain insertions define distinct roles of CLK kinases in SR protein phosphorylation.
作者信息
Bullock Alex N, Das Sanjan, Debreczeni Judit E, Rellos Peter, Fedorov Oleg, Niesen Frank H, Guo Kunde, Papagrigoriou Evangelos, Amos Ann L, Cho Suhyung, Turk Benjamin E, Ghosh Gourisankar, Knapp Stefan
机构信息
Structural Genomics Consortium, University of Oxford, Old Road Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK.
出版信息
Structure. 2009 Mar 11;17(3):352-62. doi: 10.1016/j.str.2008.12.023.
Splicing requires reversible phosphorylation of serine/arginine-rich (SR) proteins, which direct splice site selection in eukaryotic mRNA. These phosphorylation events are dependent on SR protein (SRPK) and cdc2-like kinase (CLK) families. SRPK1 phosphorylation of splicing factors is restricted by a specific docking interaction whereas CLK activity is less constrained. To understand functional differences between splicing factor targeting kinases, we determined crystal structures of CLK1 and CLK3. Intriguingly, in CLKs the SRPK1 docking site is blocked by insertion of a previously unseen helix alphaH. In addition, substrate docking grooves present in related mitogen activating protein kinases (MAPKs) are inaccessible due to a CLK specific beta7/8-hairpin insert. Thus, the unconstrained substrate interaction together with the determined active-site mediated substrate specificity allows CLKs to complete the functionally important hyperphosphorylation of splicing factors like ASF/SF2. In addition, despite high sequence conservation, we identified inhibitors with surprising isoform specificity for CLK1 over CLK3.
剪接需要富含丝氨酸/精氨酸（SR）的蛋白质进行可逆磷酸化，这些蛋白质指导真核生物mRNA中的剪接位点选择。这些磷酸化事件依赖于SR蛋白（SRPK）和类cdc2激酶（CLK）家族。剪接因子的SRPK1磷酸化受到特定对接相互作用的限制，而CLK活性的限制则较少。为了了解靶向激酶的剪接因子之间的功能差异，我们确定了CLK1和CLK3的晶体结构。有趣的是，在CLKs中，SRPK1对接位点被一个先前未见过的αH螺旋插入所阻断。此外，由于CLK特异性的β7/8发夹插入，相关的丝裂原活化蛋白激酶（MAPKs）中存在的底物对接凹槽无法进入。因此，不受限制的底物相互作用以及确定的活性位点介导的底物特异性使CLKs能够完成对剪接因子如ASF/SF2的功能上重要的过度磷酸化。此外，尽管序列保守性很高，但我们还是鉴定出了对CLK1比对CLK3具有惊人异构体特异性的抑制剂。
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