DNA damage-induced cell cycle regulation and function of novel Chk2 phosphoresidues
DNA damage-induced cell cycle regulation and function of novel Chk2 phosphoresidues
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DOI：
10.1128/mcb.00534-06
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发表时间：
2006-11-01
影响因子：
5.3
通讯作者：
Delia, Domenico
中科院分区：
文献类型：
--
作者：
Buscemi, Giacomo;Carlessi, Luigi;Delia, Domenico
Chk2激酶被DNA损伤激活，调控细胞周期阻滞、DNA修复和细胞凋亡。ataxia毛细血管扩张突变（ATM）在体内对苏氨酸68 （T68）的磷酸化启动磷酸化级联，促进Chk2的充分活性。我们在Chk2上发现了三个丝氨酸残基（S19、S33和S35），它们在电离辐射（IR）诱导的DNA双链断裂中以ATM-和nbs1依赖性、但与失联性毛细血管扩张和rad3相关的独立方式快速且特异性地被磷酸化。这些残基的磷酸化仅限于细胞周期的G(1)期，用比T68磷酸化（0.25 Gy）更高剂量的IR （bbbb1 Gy）诱导，并减少45 - 90分钟，同时Chk2自磷酸化增加。与野生型相比，在S19、S33和S35位点发生丙氨酸取代的Chk2（Chk2(S3A)）表现出二聚化受损，自磷酸化和反式磷酸化活性缺陷，促进Hdmx降解的能力降低，Hdmx是Chk2的磷酸化靶点和p53活性调节剂。此外，Chk2（S3A）未能抑制细胞生长，并在响应IR时阻止G(1)/S进展。这些发现强调了S19、S33和S35的关键作用，并认为这些磷残基可能有助于微调Chk2对DNA损伤增加量的atm依赖性反应。
Chk2 kinase is activated by DNA damage to regulate cell cycle arrest, DNA repair, and apoptosis. Phosphorylation of Chk2 in vivo by ataxia telangiectasia-mutated (ATM) on threonine 68 (T68) initiates a phosphorylation cascade that promotes the full activity of Chk2. We identified three serine residues (S19, S33, and S35) on Chk2 that became phosphorylated in vivo rapidly and exclusively in response to ionizing radiation (IR)-induced DNA double-strand breaks in an ATM- and Nbs1-dependent but ataxia telangiectasia- and Rad3-related-independent manner. Phosphorylation of these residues, restricted to the G(1) phase of the cell cycle, was induced by a higher dose of IR (> 1 Gy) than that required for phosphorylation of T68 (0.25 Gy) and declined by 45 to 90 min, concomitant with a rise in Chk2 autophosphorylation. Compared to the wild-type form, Chk2 with alanine substitutions at S19, S33, and S35 (Chk2(S3A)) showed impaired dimerization, defective auto- and trans-phosphorylation activities, and reduced ability to promote degradation of Hdmx, a phosphorylation target of Chk2 and regulator of p53 activity. Besides, Chk2(S3A) failed to inhibit cell growth and, in response to IR, to arrest G(1)/S progression. These findings underscore the critical roles of S19, S33, and S35 and argue that these phosphoresidues may serve to fine-tune the ATM-dependent response of Chk2 to increasing amounts of DNA damage.