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首页> 外文期刊>Molecular and Cellular Biology >Differential specificity for binding of retinoblastoma binding protein 2 to RB, p107, and TATA-binding protein.
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Differential specificity for binding of retinoblastoma binding protein 2 to RB, p107, and TATA-binding protein.

机译：视网膜母细胞瘤结合蛋白2与RB，p107和TATA结合蛋白结合的特异性差异。

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The growth suppressor activities of the RB and p107 products are believed to be mediated by the reversible binding of a heterogeneous family of cellular proteins to a conserved T/E1A pocket domain that is present within both proteins. To study the functional role of these interactions, we examined the properties of cellular retinoblastoma binding protein 2 (RBP2) binding to RB, p107, and the related TATA-binding protein (TBP) product. We observed that although RBP2 bound exclusively to the T/E1A pocket of p107, it could interact with RB through independent T/E1A and non-T/E1A domains and with TBP only through the non-T/E1A domain. Consistent with this observation, we found that a mutation within the Leu-X-Cys-X-Glu motif of RBP2 resulted in loss of ability to precipitate p107, while RB- and TBP-binding activities were retained. We located the non-T/E1A binding site of RBP2 on a 15-kDa fragment that is independent from the Leu-X-Cys-X-Glu motif and encodes binding activity for RB and TBP but does not interact with p107. Despite the presence of a non-T/E1A binding site, however, recombinant RBP2 retained the ability to preferentially precipitate active hypophosphorylated RB from whole-cell lysates. In addition, we found that cotransfection of RBP2 can reverse in vivo RB-mediated suppression of E2F activity. These findings confirm the differential binding specificities of the related RB, p107, and TBP proteins and support the presence of multifunctional domains on the nuclear RBP2 product which may allow complex interactions with the cellular transcription machinery.
机译：RB和p107产物的生长抑制活性被认为是由细胞蛋白异质家族与两个蛋白中均存在的保守T / E1A口袋结构域的可逆结合介导的。为了研究这些相互作用的功能作用，我们研究了细胞视网膜母细胞瘤结合蛋白2（RBP2）与RB，p107和相关TATA结合蛋白（TBP）产品结合的特性。我们观察到，尽管RBP2仅与p107的T / E1A口袋结合，但它可以通过独立的T / E1A和非T / E1A域与RB相互作用，并且仅通过非T / E1A域与TBP相互作用。与该观察结果一致，我们发现RBP2的Leu-X-Cys-X-Glu基序内的突变导致沉淀p107的能力丧失，而RB和TBP的结合活性得以保留。我们将RBP2的非T / E1A结合位点定位在15-kDa片段上，该片段独立于Leu-X-Cys-X-Glu基序，并编码RB和TBP的结合活性，但不与p107相互作用。尽管存在非T / E1A结合位点，但是，重组RBP2保留了从全细胞裂解物中优先沉淀活性次磷酸化RB的能力。此外，我们发现RBP2的共转染可以逆转体内RB介导的E2F活性的抑制。这些发现证实了相关的RB，p107和TBP蛋白的差异结合特异性，并支持核RBP2产物上多功能域的存在，这可能允许与细胞转录机制的复杂相互作用。

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