Hartley D A, Amdjadi K, Hurley T R, Lund T C, Medveczky P G, Sefton B M
Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, California, 92037, USA.
Virology. 2000 Oct 25;276(2):339-48. doi: 10.1006/viro.2000.0570.
The Tip protein of Herpesvirus saimiri strain 484C binds to and activates the Lck tyrosine protein kinase. Two sequences in the Tip protein were previously shown to be involved in binding to Lck. A proline-rich region, residues 132-141, binds to the SH3 domain of the Lck protein. We show here that the other Lck-binding domain, residues 104-113, binds to the carboxyl-terminal half of Lck and that this binding does not require the Lck SH3 domain. Mutated Tip containing only one functional Lck-binding domain can bind stably to Lck, although not as strongly as wild-type Tip. Interaction of Tip with Lck through either Lck-binding domain increases the activity of Lck in vivo. Simultaneous binding of both domains is required for maximal activation of Lck. The transient expression of Tip in T cells was found to stimulate both Stat3-dependent and NF-AT-dependent transcription. Mutant forms of Tip lacking one or the other of the two Lck-binding domains retained the ability to stimulate Stat3-dependent transcription. Tip lacking the proline-rich Lck-binding domain exhibited almost wild-type activity in this assay. In contrast, ablation of either Lck-binding domain abolished the ability of Tip to stimulate NF-AT-dependent transcription. Full biological activity of Tip, therefore, appears to require both Lck-binding domains.
猴疱疹病毒484C株的Tip蛋白与Lck酪氨酸蛋白激酶结合并激活它。Tip蛋白中的两个序列先前已被证明参与与Lck的结合。一个富含脯氨酸的区域，即第132 - 141位氨基酸残基，与Lck蛋白的SH3结构域结合。我们在此表明，另一个Lck结合结构域，即第104 - 113位氨基酸残基，与Lck的羧基末端一半结合，并且这种结合不需要Lck的SH3结构域。仅含有一个功能性Lck结合结构域的突变型Tip可以稳定地与Lck结合，尽管结合强度不如野生型Tip。Tip通过任一Lck结合结构域与Lck的相互作用都会增加Lck在体内的活性。两个结构域同时结合是Lck最大激活所必需的。发现在T细胞中瞬时表达Tip会刺激Stat3依赖性和NF-AT依赖性转录。缺乏两个Lck结合结构域中任何一个的Tip突变形式保留了刺激Stat3依赖性转录的能力。在该实验中，缺乏富含脯氨酸的Lck结合结构域的Tip表现出几乎野生型的活性。相反，去除任一Lck结合结构域都会消除Tip刺激NF-AT依赖性转录的能力。因此，Tip的完整生物学活性似乎需要两个Lck结合结构域。
