The growth factor granulin interacts with cyclin T1 and modulates P-TEFb-dependent transcription
The growth factor granulin interacts with cyclin T1 and modulates P-TEFb-dependent transcription
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DOI：
10.1128/mcb.23.5.1688-1702.2003
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发表时间：
2003-03-01
影响因子：
5.3
通讯作者：
Pe'ery, T
中科院分区：
文献类型：
--
作者：
Hoque, M;Young, TM;Pe'ery, T
细胞周期蛋白T1与激酶CDK9一起，是转录延伸因子P-TEFb的一个组成部分，它结合人类免疫缺陷病毒1型（HIV-1）反激活子Tat。P-TEFb通过磷酸化RNA聚合酶II的羧基末端结构域（CTD）来促进转录。细胞周期蛋白T1是一个特别大的细胞周期蛋白，因此是与调节蛋白相互作用的候选蛋白。我们发现颗粒蛋白是一种细胞周期蛋白t1相互作用蛋白，在转染细胞中抑制HIV-1启动子的表达。颗粒是一种含有富含半胱氨酸基序重复序列的有丝分裂生长因子，以前曾报道过与Tat相互作用。我们发现颗粒蛋白在体内和体外与细胞周期蛋白T1和Tat形成稳定的复合物。颗粒蛋白结合到细胞周期蛋白T1的富含组氨酸的区域，最近发现它与CTD结合，但不与细胞周期蛋白T2结合。颗粒蛋白与P-TEFb的结合抑制了CTD肽的磷酸化。颗粒蛋白的表达抑制了Tat的转激活，而系留实验表明，这种作用至少部分是由于在没有Tat的情况下对周期蛋白T1的直接作用。此外，颗粒蛋白是CDK9的底物，而不是其他转录相关激酶CDK7和CDK8的底物。因此，颗粒蛋白是一种与细胞周期蛋白T1相互作用抑制转录的细胞蛋白。
Cyclin T1, together with the kinase CDK9, is a component of the transcription elongation factor P-TEFb which binds the human immunodeficiency virus type 1 (HIV-1) transactivator Tat. P-TEFb facilitates transcription by phosphorylating the carboxy-terminal domain (CTD) of RNA polymerase II. Cyclin T1 is an exceptionally large cyclin and is therefore a candidate for interactions with regulatory proteins. We identified granulin as a cyclin T1-interacting protein that represses expression from the HIV-1 promoter in transfected cells. The granulins, mitogenic growth factors containing repeats of a cysteine-rich motif, were reported previously to interact with Tat. We show that granulin formed stable complexes in vivo and in vitro with cyclin T1 and Tat. Granulin bound to the histidine-rich domain of cyclin T1, which was recently found to bind to the CTD, but not to cyclin T2. Binding of granulin to P-TEFb inhibited the phosphorylation of a CTD peptide. Granulin expression inhibited Tat transactivation, and tethering experiments showed that this effect was due, at least in part, to a direct action on cyclin T1 in the absence of Tat. In addition, granulin was a substrate for CDK9 but not for the other transcription-related kinases CDK7 and CDK8. Thus, granulin is a cellular protein that interacts with cyclin T1 to inhibit transcription.