Boehm Manfred, Yoshimoto Takanobu, Crook Martin F, Nallamshetty Shriram, True Andrea, Nabel Gary J, Nabel Elizabeth G
Cardiovascular Branch, NHLBI, National Institutes of Health, Bethesda, MD 20892, USA.
EMBO J. 2002 Jul 1;21(13):3390-401. doi: 10.1093/emboj/cdf343.
The cyclin-dependent kinase inhibitor, p27(Kip1), which regulates cell cycle progression, is controlled by its subcellular localization and subsequent degradation. p27(Kip1) is phosphorylated on serine 10 (S10) and threonine 187 (T187). Although the role of T187 and its phosphorylation by Cdks is well-known, the kinase that phosphorylates S10 and its effect on cell proliferation has not been defined. Here, we identify the kinase responsible for S10 phosphorylation as human kinase interacting stathmin (hKIS) and show that it regulates cell cycle progression. hKIS is a nuclear protein that binds the C-terminal domain of p27(Kip1) and phosphorylates it on S10 in vitro and in vivo, promoting its nuclear export to the cytoplasm. hKIS is activated by mitogens during G(0)/G(1), and expression of hKIS overcomes growth arrest induced by p27(Kip1). Depletion of KIS using small interfering RNA (siRNA) inhibits S10 phosphorylation and enhances growth arrest. p27(-/-) cells treated with KIS siRNA grow and progress to S/G(2 )similar to control treated cells, implicating p27(Kip1) as the critical target for KIS. Through phosphorylation of p27(Kip1) on S10, hKIS regulates cell cycle progression in response to mitogens.
细胞周期蛋白依赖性激酶抑制剂p27（Kip1）可调节细胞周期进程，其受亚细胞定位及随后的降解过程控制。p27（Kip1）在丝氨酸10（S10）和苏氨酸187（T187）位点发生磷酸化。尽管T187及其被细胞周期蛋白依赖性激酶（Cdks）磷酸化的作用已为人熟知，但磷酸化S10的激酶及其对细胞增殖的影响尚未明确。在此，我们确定负责S10磷酸化的激酶为人激酶相互作用微管相关蛋白（hKIS），并表明它可调节细胞周期进程。hKIS是一种核蛋白，可结合p27（Kip1）的C末端结构域，并在体外和体内使p27（Kip1）的S10位点磷酸化，促进其从细胞核输出到细胞质。hKIS在G（0）/G（1）期被有丝分裂原激活，hKIS的表达可克服由p27（Kip1）诱导的生长停滞。使用小干扰RNA（siRNA）耗尽KIS可抑制S10磷酸化并增强生长停滞。用KIS siRNA处理的p27（-/-）细胞生长并进入S/G（2）期，类似于用对照处理的细胞，这表明p27（Kip1）是KIS的关键靶点。通过使p27（Kip1）的S10位点磷酸化，hKIS可响应有丝分裂原调节细胞周期进程。
