Inhibition of lens fiber cell morphogenesis by expression of a mutant SV40 large T antigen that binds CREB-binding protein/p300 but not pRb
Inhibition of lens fiber cell morphogenesis by expression of a mutant SV40 large T antigen that binds CREB-binding protein/p300 but not pRb
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DOI：
10.1074/jbc.m311678200
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发表时间：
2004-04-23
影响因子：
4.8
通讯作者：
Overbeek, PA
中科院分区：
文献类型：
--
作者：
Chen, Q;Liang, DC;Overbeek, PA
猿猴病毒（SV）40大T抗原既能诱导肿瘤，又能抑制细胞分化。目前尚不清楚这些细胞变化是对蛋白质的同义反应、连续反应还是不同反应。已知 T 抗原可与 p53、视网膜母细胞瘤 (Rb) 肿瘤抑制蛋白家族以及其他细胞蛋白（例如 p300 家族成员）结合。为了测试 SV40 大 T 抗原是否在没有细胞周期诱导的情况下抑制体内细胞分化，我们培育了在晶状体中表达 SV40 早期区域突变版本的转基因小鼠。这种突变体，我们称之为 E107KDelta，具有消除小 t 抗原合成的缺失和导致丧失与 Rb 家族成员结合的能力的点突变 (E107K)。在胚胎第 15.5 天 (E15.5)，转基因晶状体在晶状体纤维细胞分化方面表现出显着的缺陷。纤维细胞进入有丝分裂后，但不能正常伸长。这些细胞的β-和γ-晶状体蛋白的表达显着减少。由于 CBP 和 p300 是晶状体蛋白基因表达的共激活剂，因此我们分析了 E107KDelta 和 CBP/p300 之间的相互作用。我们的研究表明，在没有 pRb 失活的情况下，SV40 大 T 抗原可以抑制细胞分化，并且消除与 pRb 结合的突变可能会增强大 T 抗原与 CBP/p300 的相互作用。
Simian virus (SV) 40 large T antigen can both induce tumors and inhibit cellular differentiation. It is not clear whether these cellular changes are synonymous, sequential, or distinct responses to the protein. T antigen is known to bind to p53, to the retinoblastoma (Rb) family of tumor suppressor proteins, and to other cellular proteins such as p300 family members. To test whether SV40 large T antigen inhibits cellular differentiation in vivo in the absence of cell cycle induction, we generated transgenic mice that express in the lens a mutant version of the early region of SV40. This mutant, which we term E107KDelta, has a deletion that eliminates synthesis of small t antigen and a point mutation (E107K) that results in loss of the ability to bind to Rb family members. At embryonic day 15.5 (E15.5), the transgenic lenses show dramatic defects in lens fiber cell differentiation. The fiber cells become post-mitotic, but do not elongate properly. The cells show a dramatic reduction in expression of their beta- and gamma-crystallins. Because CBP and p300 are co-activators for crystallin gene expression, we assayed for interactions between E107KDelta and CBP/p300. Our studies demonstrate that cellular differentiation can be inhibited by SV40 large T antigen in the absence of pRb inactivation, and that interaction of large T antigen with CBP/p300 may be enhanced by a mutation that eliminates the binding to pRb.