Inhibition of cyclin D1 phosphorylation on threonine-286 prevents its rapid degradation via the ubiquintin-proteasome pathway
Inhibition of cyclin D1 phosphorylation on threonine-286 prevents its rapid degradation via the ubiquintin-proteasome pathway
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DOI：
10.1101/gad.11.8.957
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发表时间：
1997-04-15
影响因子：
10.5
通讯作者：
Sherr, CJ
中科院分区：
文献类型：
--
作者：
Diehl, JA;Zindy, F;Sherr, CJ
D型G1细胞周期蛋白的表达及其与其催化伴侣细胞周期蛋白依赖性激酶4和6（CDK 4和CDK 6）组装成活性全酶复合物受生长因子诱导的信号调节。反过来，细胞周期蛋白D依赖性激酶在细胞周期的中期至晚期G（1）期触发视网膜母细胞瘤（Rb）蛋白磷酸化的能力使得Rb的生长抑制功能的失活成为促分裂原依赖性步骤。D型细胞周期蛋白作为生长因子传感器的能力不仅取决于它们被有丝分裂原快速诱导，而且还取决于它们固有的不稳定性，这确保了它们在缺乏生长因子的细胞中急剧降解。然而，D型细胞周期蛋白的周转机制尚未阐明。我们现在表明，细胞周期蛋白D1的营业额是由泛素化和蛋白酶体降解，这是积极调节细胞周期蛋白D1磷酸化苏氨酸-286。尽管“游离"或CDK 4结合的细胞周期蛋白D1分子本质上是不稳定的，（t1/2 < 30分钟），含有丙氨酸取代苏氨酸-286的细胞周期蛋白D1突变体（T286 A）在体外系统或体内不能进行有效的聚泛素化，并且当在静止或增殖的小鼠成纤维细胞中诱导表达时，其显著稳定（t1/2类似于3.5小时）。在昆虫Sf 9细胞中，细胞周期蛋白D1在苏氨酸-286上的磷酸化也发生，尽管该过程通过细胞周期蛋白D1与CDK 4的结合而显著增强，但它不依赖于CDK 4的催化活性。这意味着另一种激酶可以磷酸化细胞周期蛋白D1，以加速其破坏，并指出另一种手段，细胞周期蛋白D依赖性激酶的活性可能是外源性调节。
The expression of D-type G1 cyclins and their assembly with their catalytic partners, the cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), into active holoenzyme complexes are regulated by growth factor-induced signals. In turn, the ability of cyclin D-dependent kinases to trigger phosphorylation of the retinoblastoma (Rb) protein in the mid- to late G(1) phase of the cell cycle makes the inactivation of Rb's growth suppressive function a mitogen-dependent step. The ability of D-type cyclins to act as growth factor sensors depends not only on their rapid induction by mitogens but also on their inherent instability, which ensures their precipitous degradation in cells deprived of growth factors. However, the mechanisms governing the turnover of D-type cyclins have not yet been elucidated. We now show that cyclin D1 turnover is governed by ubiquitination and proteasomal degradation, which are positively regulated by cyclin D1 phosphorylation on threonine-286. Although ''free'' or CDK4-bound cyclin D1 molecules are intrinsically unstable (t1/2 < 30 min), a cyclin D1 mutant (T286A) containing an alanine for threonine-286 substitution fails to undergo efficient polyubiquitination in an in vitro system or in vivo, and it is markedly stabilized (t1/2 similar to 3.5 hr) when inducibly expressed in either quiescent or proliferating mouse fibroblasts. Phosphorylation of cyclin D1 on threonine-286 also occurs in insect Sf9 cells, and although the process is enhanced significantly by the binding of cyclin D1 to CDK4, it does not depend on CDK4 catalytic activity. This implies that another kinase can phosphorylate cyclin D1 to accelerate its destruction and points to yet another means by which cyclin D-dependent kinase activity may be exogenously regulated.