Habib S, Hasnain S E
Eukaryotic Gene Expression Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
J Biol Chem. 1996 Nov 8;271(45):28250-8. doi: 10.1074/jbc.271.45.28250.
We recently demonstrated that the Autographa californica multinucleocapsid nuclear polyhedrosis virus homologous region (hr1) enhances transcription from the viral polyhedrin promoter and also functions as a putative origin of replication (ori). Hr1, carrying five 28-base pair core palindrome units, has also been mapped with respect to its enhancer and ori functions (Habib, S., Pandey, S., Chatterji, U., Burma, S., Ahmad, R., Jain, A., and Hasnain, S. E. (1996) DNA Cell Biol. 15, 737-747). A 38-kDa host factor termed hr1-binding protein (hr1-BP) binds with high specificity and affinity (Kd approximately 6.5 x 10(-11) M) to functionally important motifs within hr1. The core palindrome as well as sequences immediately flanking it are required for this interaction. Divalent cations are not essential, and ionic interactions play only a minor role in complex formation. hr1-BP binds through the minor groove of the double helix to multiple sites within hr1, and binding occurs as a function of the number of modules within hr1. Phosphorylation of hr1-BP is important for host factor-hr1 interaction. Hr1-BP differs in several respects from the other host factor, polyhedrin promoter-binding protein, described previously (Burma, S., Mukherjee, B., Jain, A., Habib, S., and Hasnain, S. E. (1994) J. Biol. Chem. 269, 2750-2757). When hr1-BP was sequestered out, in vivo, by a plasmid carrying hr1 alone, the hr1-mediated enhancement of reporter expression was abolished, demonstrating that the binding of hr1-BP may be crucial for the enhancer activity of the dual function hr1 element.
我们最近证明，苜蓿银纹夜蛾多核衣壳核型多角体病毒同源区域（hr1）可增强病毒多角体蛋白启动子的转录，并且还作为一个假定的复制起点（ori）发挥作用。携带五个28碱基对核心回文单元的hr1，也已就其增强子和ori功能进行了定位（哈比卜，S.，潘迪，S.，查特吉，U.，缅甸，S.，艾哈迈德，R.，贾因，A.，和哈桑奈恩，S.E.（1996年）《DNA细胞生物学》15卷，737 - 747页）。一种名为hr1结合蛋白（hr1 - BP）的38 kDa宿主因子以高特异性和亲和力（解离常数约为6.5×10⁻¹¹ M）与hr1内功能重要的基序结合。这种相互作用需要核心回文序列及其紧邻的侧翼序列。二价阳离子并非必需，离子相互作用在复合物形成中仅起次要作用。hr1 - BP通过双螺旋的小沟与hr1内的多个位点结合，并且结合是hr1内模块数量的函数。hr1 - BP的磷酸化对于宿主因子 - hr1相互作用很重要。hr1 - BP在几个方面与先前描述的另一种宿主因子多角体蛋白启动子结合蛋白不同（缅甸，S.，穆克吉，B.，贾因，A.，哈比卜，S.，和哈桑奈恩，S.E.（1994年）《生物化学杂志》269卷，2750 - 2757页）。当在体内通过仅携带hr1的质粒将hr1 - BP隔离出来时，hr1介导的报告基因表达增强被消除，这表明hr1 - BP的结合对于双功能hr1元件的增强子活性可能至关重要。
