Ma Yunmei, Pannicke Ulrich, Schwarz Klaus, Lieber Michael R
Norris Comprehensive Cancer Center, Rm. 5428, Departments of Biochemistry & Molecular Biology, Pathology, Biological Sciences, and Molecular Microbiology & Immunology, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA.
Cell. 2002 Mar 22;108(6):781-94. doi: 10.1016/s0092-8674(02)00671-2.
Mutations in the Artemis protein in humans result in hypersensitivity to DNA double-strand break-inducing agents and absence of B and T lymphocytes (radiosensitive severe combined immune deficiency [RS-SCID]). Here, we report that Artemis forms a complex with the 469 kDa DNA-dependent protein kinase (DNA-PKcs) in the absence of DNA. The purified Artemis protein alone possesses single-strand-specific 5' to 3' exonuclease activity. Upon complex formation, DNA-PKcs phosphorylates Artemis, and Artemis acquires endonucleolytic activity on 5' and 3' overhangs, as well as hairpins. Finally, the Artemis:DNA-PKcs complex can open hairpins generated by the RAG complex. Thus, DNA-PKcs regulates Artemis by both phosphorylation and complex formation to permit enzymatic activities that are critical for the hairpin-opening step of V(D)J recombination and for the 5' and 3' overhang processing in nonhomologous DNA end joining.
人类阿耳忒弥斯蛋白的突变会导致对DNA双链断裂诱导剂过敏，且缺乏B淋巴细胞和T淋巴细胞（放射敏感严重联合免疫缺陷[RS-SCID]）。在此，我们报告阿耳忒弥斯在无DNA的情况下与469 kDa的DNA依赖性蛋白激酶（DNA-PKcs）形成复合物。纯化后的阿耳忒弥斯蛋白单独具有单链特异性5'至3'核酸外切酶活性。复合物形成后，DNA-PKcs使阿耳忒弥斯磷酸化，阿耳忒弥斯获得对5'和3'突出端以及发夹结构的内切核酸酶活性。最后，阿耳忒弥斯：DNA-PKcs复合物可打开由RAG复合物产生的发夹结构。因此，DNA-PKcs通过磷酸化和复合物形成来调节阿耳忒弥斯，以使其具备对V(D)J重组的发夹打开步骤以及非同源DNA末端连接中5'和3'突出端加工至关重要的酶活性。
