Brand S R, Kobayashi R, Mathews M B
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11742, USA.
J Biol Chem. 1997 Mar 28;272(13):8388-95. doi: 10.1074/jbc.272.13.8388.
We demonstrate that the interferon-induced, double-stranded (ds) RNA-activated kinase, PKR, is able to bind to and phosphorylate the human immunodeficiency virus type 1 (HIV-1) trans-activating protein, Tat. Furthermore, Tat can inhibit the activation and activity of the kinase. Phosphorylation of Tat by PKR is dependent on the prior activation of PKR by dsRNA and occurs on serine and threonine residues adjacent to the basic region important for TAR RNA binding and Tat function. Activated PKR efficiently phosphorylates both the two-exon form of Tat (Tat-86) and the single exon form (Tat-72). Mutagenesis indicates that the interaction between PKR and Tat requires the RNA-binding region of Tat. Tat competes with eukaryotic initiation factor 2, a well-characterized substrate of PKR, for phosphorylation by activated PKR. Tat also inhibits the autophosphorylation of PKR by dsRNA. This biochemical evidence of an intimate relationship between Tat, an important regulator of HIV transcription, and PKR, a pleiotropic cellular regulator, may provide insights into HIV-1 pathogenesis and, more generally, virus/host interactions.
我们证明，干扰素诱导的双链（ds）RNA激活激酶PKR能够结合并磷酸化人免疫缺陷病毒1型（HIV-1）反式激活蛋白Tat。此外，Tat能够抑制该激酶的激活及其活性。PKR对Tat的磷酸化依赖于dsRNA对PKR的预先激活，且发生在与对TAR RNA结合和Tat功能至关重要的碱性区域相邻的丝氨酸和苏氨酸残基上。激活的PKR能有效地磷酸化Tat的双外显子形式（Tat-86）和单外显子形式（Tat-72）。诱变表明，PKR与Tat之间的相互作用需要Tat的RNA结合区域。Tat与真核起始因子2（PKR的一个已充分研究的底物）竞争被激活的PKR磷酸化。Tat还抑制dsRNA诱导的PKR自磷酸化。HIV转录的重要调节因子Tat与多效性细胞调节因子PKR之间这种密切关系的生化证据，可能为深入了解HIV-1发病机制以及更广泛的病毒/宿主相互作用提供线索。
