Role of LXCXE motif-dependent interactions in the activity of the retinoblastoma protein
Role of LXCXE motif-dependent interactions in the activity of the retinoblastoma protein
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DOI：
10.1038/sj.onc.1204793
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发表时间：
2001-09-27
期刊：
影响因子：
8
通讯作者：
La Thangue, NB
中科院分区：
文献类型：
--
作者：
Chan, HM;Smith, L;La Thangue, NB
通过pRb控制细胞周期需要口袋结构域的完整性，口袋结构域是与多种蛋白质（包括含有E2 F和LXCXE基序的蛋白质）相互作用所必需的区域。通过对pRb晶体结构的了解，我们制备了一组pRb突变体衍生物，其中区分LXCXE肽结合结构域的赖氨酸残基簇被系统地突变。其中一种突变衍生物Rb 6A与HPV E7、cyclinD 1和HDAC 2的LXCXE依赖性相互作用显著降低，但保留了与E2 F的LXCXE非依赖性结合。与这些结果一致，Rb 6A可以下调E2 F-1依赖的不同E2 F应答启动子的激活，但在Rb依赖的抑制中受到损害。最重要的是，Rb 6A保留了野生型生长停滞活性和与野生型pRb相似的集落形成活性。与这些结果一致的是，将HDAC 2直接靶向E2 F应答启动子作为E2 F/HDAC杂合蛋白未能实现细胞周期阻滞。这些结果表明，LXCXE依赖的相互作用是不是必不可少的pRb发挥生长停滞。
Cell cycle control by pRb requires the integrity of the pocket domain, which is a region necessary for interactions with a variety of proteins, including E2F and LXCXE-motif containing proteins. Through knowledge of the crystal structure of pRb we have prepared a panel of pRb mutant derivatives in which a cluster of lysine residues that demark the LXCXE peptide binding domain were systematically mutated. One of the mutant derivatives, Rb6A, exhibits significantly reduced LXCXE-dependent interactions with HPV E7, cyclinD1 and HDAC2, but retained LXCXE-independent binding to E2F. Consistent with these results, Rb6A could down-regulate E2F-1-dependent activation of different E2F responsive promoters, but was compromised in Rb-dependent repression. Most importantly, Rb6A retained wild-type growth arrest activity, and colony forming activity similar to wild-type pRb. It is compatible with these results that directly targeting HDAC2 to E2F responsive promoters as an E2F/HDAC hybrid protein failed to effect cell cycle arrest. These results suggest that LXCXE-dependent interactions are not essential for pRb to exert growth arrest.