STRUCTURE/FUNCTION OF A DNA ACTIVATED PROTEIN KINASE FROM HELA CELLS

一种新的双链DNA激活蛋白激酶（DNA-PK）已被发现， 从HeLa细胞中大量纯化。几种单克隆抗体具有 它能特异性地抑制酶的活性， 蛋白质印迹上的单个350 kDa多肽。将纯化DNA-PK， 使用FPLC和免疫亲和色谱的均一性，以及其独特的 将研究生物化学性质。酶与DNA的相互作用 将通过描述其对一级序列的要求来探讨， 活化多核苷酸的二级结构。特异性试剂 和分析将被开发，包括额外的单克隆和 多克隆抗体、合成肽底物和核酸 probes.后者将使用cDNA表达进行分子克隆 用单克隆抗体探测的文库。 这些试剂将用于 以确定种间分布和细胞内定位 的DNA-PK的表达，并研究DNA-PK表达的调节， 基因水平。DNA-PK的生物学功能将通过以下方法阐明： 检查（l）其与其他细胞和病毒蛋白的相互作用， 使用免疫共沉淀和蛋白质印迹;和（2）其存在 和活性在细胞周期的不同阶段，使用同步 通过离心淘析和通过离心淘析获得的HeLa细胞群体， 代谢抑制 由于双链DNA的非凡激活作用， 通过DNA-PK的底物蛋白的磷酸化， 细胞内的DNA-PK可能是染色质或蛋白质， 染色质。了解分子结构、机制和 因此，这种迄今未知类型的蛋白激酶的功能可能 对理解基因活性的调控具有重要意义 和/或染色质动力学，包括相关的分子过程 DNA复制、重组、DNA修复和细胞分裂。因此 DNA-PK和/或相关蛋白激酶的生物学功能可以 影响多种人类疾病，包括肿瘤，发育 异常和对病毒感染的反应。

A novel, double-stranded DNA-activated protein kinase (DNA-PK) has been extensively purified from HeLa cells. Several monoclonal antibodies have been made which specifically inhibit the enzyme's activity and recognize a single 350 kDa polypeptide on Western blots. DNA-PK will be purified to homogeneity using FPLC and immunoaffinity chromatography, and its unique biochemical properties will be studied. Interaction of the enzyme with DNA will be probed by characterizing its requirements for primary sequence and secondary structure of the activating polynucleotide. Specific reagents and assays will be developed, including additional monoclonal and polyclonal antibodies, synthetic peptide substrates, and nucleic acid probes. The latter will be molecularly cloned using cDNA expression libraries probed with monoclonal antibodies. These reagents will be used to determine the interspecies distribution and intracellular localization of DNA-PK, and also to study the regulation of DNA-PK expression at the genetic level. The biologic function(s) of DNA-PK will be elucidated by examining (l) its interactions with other cellular and viral proteins, using co-immunoprecipitation and Western blotting; and (2) its presence and activity at different stages of the cell cycle using synchronous populations of HeLa cells obtained by centrifugal elutriation and by metabolic inhibition. Because of the extraordinary activating effect of double-stranded DNA on the phosphorylation of substrate proteins by DNA-PK, the site of action of DNA-PK within the cell is likely to be chromatin or proteins that interact with chromatin. Understanding the molecular structure, mechanism and function of this heretofore unknown type of protein kinase could therefore have major significance for understanding the regulation of gene activity and/or chromatin dynamics, including the molecular processes associated with DNA replication, recombination, DNA repair, and cell division. Thus the biological function of DNA-PK and/or related protein kinases could impact a variety of human diseases, including neoplasia, developmental abnormalities, and the response to viral infection.