Gupta Vishal, Huang Xu, Patel Rekha C
Department of Biological Sciences, University of South Carolina, 700 Sumter Street, Columbia, SC 29208, USA.
Virology. 2003 Oct 25;315(2):283-91. doi: 10.1016/s0042-6822(03)00589-0.
PKR is an interferon(IFN)-induced, serine-threonine protein kinase, which plays a crucial role in IFN's antiviral and antiproliferative actions. The three known activators of PKR are dsRNA, heparin, and PACT. PACT activates PKR by direct protein-protein interaction in response to cellular stress. The human TAR (trans-activating region)-binding protein (TRBP), which is very homologous to PACT, also interacts with PKR, leading to an inhibition of PKR activity. Since these two highly homologous proteins have opposite effects on PKR, we examined if they interact with PKR differently by assaying their interaction with various point mutants of PKR. Our results indicate that TRBP and PACT interact with PKR through the same residues, and no differences were identified in these two interactions. Domain swap experiments between PACT and TRBP indicated that the inhibitory effects of TRBP on PKR activity are mediated through its carboxy-terminal residues, which contain TRBP's third dsRNA-binding motif.
PKR是一种干扰素（IFN）诱导的丝氨酸-苏氨酸蛋白激酶，在IFN的抗病毒和抗增殖作用中起关键作用。已知的PKR三种激活剂是双链RNA（dsRNA）、肝素和PACT。PACT通过响应细胞应激的直接蛋白质-蛋白质相互作用激活PKR。与PACT高度同源的人反式激活应答元件（TAR）结合蛋白（TRBP）也与PKR相互作用，导致PKR活性受到抑制。由于这两种高度同源的蛋白质对PKR具有相反的作用，我们通过检测它们与PKR各种点突变体的相互作用，研究它们与PKR的相互作用是否存在差异。我们的结果表明，TRBP和PACT通过相同的残基与PKR相互作用，在这两种相互作用中未发现差异。PACT和TRBP之间的结构域交换实验表明，TRBP对PKR活性的抑制作用是通过其羧基末端残基介导的，该残基包含TRBP的第三个dsRNA结合基序。
