Cyclin D1/Cdk4 regulates retinoblastoma protein-mediated cell cycle arrest by site-specific phosphorylation
Cyclin D1/Cdk4 regulates retinoblastoma protein-mediated cell cycle arrest by site-specific phosphorylation
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DOI：
10.1091/mbc.8.2.287
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发表时间：
1997-02-01
影响因子：
3.3
通讯作者：
Goodrich, DW
中科院分区：
文献类型：
--
作者：
ConnellCrowley, L;Harper, JW;Goodrich, DW
视网膜母细胞瘤蛋白（pRb）抑制细胞周期的进展。虽然当G（1）细胞周期蛋白依赖性激酶（Cdks）活跃时pRb被磷酸化，但pRb调节的潜在机制尚不清楚。细胞周期蛋白D1/Cdk 4的体外磷酸化导致pRb在基于显微注射的体内细胞周期测定中失活。相反，在该测定中，尽管广泛的磷酸化并转化为缓慢迁移的“过度磷酸化”形式，但与A型或E型细胞周期蛋白复合的Cdk 2或Cdk 3对pRb的磷酸化不足以抑制pRb的功能。磷酸化对pRb功能的不同影响与不同位点的修饰一致。丝氨酸795被Cdk 4有效地磷酸化，即使在细胞周期蛋白D中不存在完整的LXCXE基序的情况下，但不是由Cdk 2或Cdk 3。丝氨酸795突变为丙氨酸防止pRb失活的Cdk 4磷酸化在显微注射测定。这项研究确定了一个残基，其磷酸化是关键的pRb介导的生长抑制的失活，它表明，过度磷酸化和pRb的失活不一定是同义词。
The retinoblastoma protein (pRb) inhibits progression through the cell cycle. Although pRb is phosphorylated when G(1) cyclin-dependent kinases (Cdks) are active, the mechanisms underlying pRb regulation are unknown. In vitro phosphorylation by cyclin D1/Cdk4 leads to inactivation of pRb in a microinjection-based in vivo cell cycle assay. In contrast, phosphorylation of pRb by Cdk2 or Cdk3 in complexes with A- or E-type cyclins is not sufficient to inactivate pRb function in this assay, despite extensive phosphorylation and conversion to a slowly migrating ''hyperphosphorylated form.'' The differential effects of phosphorylation on pRb function coincide with modification of distinct sets of sites. Serine 795 is phosphorylated efficiently by Cdk4, even in the absence of an intact LXCXE motif in cyclin D, but not by Cdk2 or Cdk3. Mutation of serine 795 to alanine prevents pRb inactivation by Cdk4 phosphorylation in the microinjection assay. This study identifies a residue whose phosphorylation is critical for inactivation of pRb-mediated growth suppression, and it indicates that hyperphosphorylation and inactivation of pRb are not necessarily synonymous.