Distinct action of the retinoblastoma pathway on the DNA replication machinery defines specific roles for cyclin-dependent kinase complexes in prereplication complex assembly and S-phase progression (Retracted Article)
Distinct action of the retinoblastoma pathway on the DNA replication machinery defines specific roles for cyclin-dependent kinase complexes in prereplication complex assembly and S-phase progression (Retracted Article)
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DOI：
10.1128/mcb.00045-06
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发表时间：
2006-10-01
影响因子：
5.3
通讯作者：
Knudsen, Erik S.
中科院分区：
文献类型：
--
作者：
Braden, Wesley A.;Lenihan, Jon M.;Knudsen, Erik S.
视网膜母细胞瘤（RB）和p16ink4a肿瘤抑制因子被认为在一个线性途径中发挥作用，该途径在大部分人类癌症中功能失活。最近的研究表明，RB作为抑制异常增殖和控制基因组稳定性的手段，在调节S期中起关键作用。在这里，我们证明了一个新的作用，p16ink4a在复制控制，是从RB不同。具体而言，p16ink4a通过抑制G中的微型染色体维持（MCM）蛋白加载来破坏复制前复合物组装，而RB被发现通过衰减PCNA功能来破坏S期的复制。p16ink4a对复制前复合物的影响依赖于RB的存在和细胞周期蛋白依赖性激酶（CDK）活性的下调。引人注目的是，CDK2活性的抑制不足以阻止MCM蛋白加载到染色质上，这支持了一种模型，其中多个G，CDK复合物的复合作用调节复制前复合物组装。此外，p16ink4a减弱了组装因子Cdt1和Cdc6的水平。这两个许可因子的强制表达足以恢复复制前复合物的组装，但由于持续缺乏PCNA功能而未能促进S期进展。结合，这些数据表明，RB和p16ink4a功能通过不同的途径，以抑制复制机制，并提供证据表明，逐步调节CDK活性接口与复制机制在两个离散的执行点。
The retinoblastoma (RB) and p16ink4a tumor suppressors are believed to function in a linear pathway that is functionally inactivated in a large fraction of human cancers. Recent studies have shown that RB plays a critical role in regulating S phase as a means for suppressing aberrant proliferation and controlling genome stability. Here, we demonstrate a novel role for p16ink4a in replication control that is distinct from that of RB. Specifically, p16ink4a disrupts prereplication complex assembly by inhibiting mini-chromosome maintenance (MCM) protein loading in G, while RB was found to disrupt replication in S phase through attenuation of PCNA function. This influence of p16ink4a on the prereplication complex was dependent on the presence of RB and the downregulation of cyclin-dependent kinase (CDK) activity. Strikingly, the inhibition of CDK2 activity was not sufficient to prevent the loading of MCM proteins onto chromatin, which supports a model wherein the composite action of multiple G, CDK complexes regulates prereplication complex assembly. Additionally, p16ink4a attenuated the levels of the assembly factors Cdt1 and Cdc6. The enforced expression of these two licensing factors was sufficient to restore the assembly of the prereplication complex yet failed to promote S-phase progression due to the continued absence of PCNA function. Combined, these data reveal that RB and p16ink4a function through distinct pathways to inhibit the replication machinery and provide evidence that stepwise regulation of CDK activity interfaces with the replication machinery at two discrete execution points.