Binding of p300/CBP co-activators by polyoma large T antigen.

Small DNA tumor viruses such as simian virus 40 (SV40) and polyomavirus (Py) take advantage of host cell proteins to transcribe and replicate their DNA. Interactions between the viral T antigens and host proteins result in cell transformation and tumor induction. Large T antigen of SV40 interacts with p53, pRb/p107/p130 family members, and the cyclic AMP-responsive element-binding protein (CREB)-binding protein (CBP)/p300. Py large T antigen is known to interact only with pRb and p300 among these proteins. Here we report that Py large T binds to CBP in vivo and in vitro. In co-transfection assays, Py large T inhibits the co-activation functions of CBP/p300 in CREB-mediated transactivation but not in NF-kappa B-mediated transactivation. p53 appears not to be involved in the functions of CREB-mediated transactivation and is not essential for large T:CBP interaction. Mutations introduced into a region of Py large T with homology to adenovirus E1A and SV40 large T prevent binding to the co-activators. These mutant large T antigens fail to inhibit CREB-mediated transactivation. The CBP/p300-binding Py mutants are able to transform established rat embryo fibroblasts but are restricted in their ability to induce tumors in the newborn mouse, indicating that interaction of large T with the co-activators may be essential for virus replication and spread in the intact host.     

Effect of trichostatin A on fertilization and embryo development during extended culture of mouse oocyte

We performed this study to investigate the effect of histone deacetylase inhibition during extended culture of in vitro matured mouse oocytes. In vitro matured mouse (BDF1) oocytes were cultured in vitro for 6, 12, and 24 h, respectively, and then inseminated. During in vitro culture for 6 and 12 h, two doses of trichostatin A (TSA), a histone deacetylase inhibitor, were added (100 nM and 500 nM) to the culture medium and the oocytes were then inseminated. During the 24-h in vitro culture, two doses of TSA were added (100 nM and 500 nM) to the medium and the oocytes were activated with 10 mM SrCl2. After the 6-h culture, the fertilization rate was similar to that of the control group, but the blastocyst formation rate was significantly decreased. After the 12-h culture, both the fertilization and blastocyst formation rates were significantly decreased. After the 24-h culture, total fertilization failure occurred. In the oocytes cultured for 6 and 12 h, the fertilization and blastocyst formation rates did not differ between the TSA-supplemented and control groups. Although extended culture of the mouse oocytes significantly affected their fertilization and embryo development, TSA supplementation did not overcome their decreased developmental potential.     

膜去极化与cAMP在胰岛细胞株HIT中诱导CBP片段的转录活性

为了研究 Ｃ Ｂ Ｐ在胰岛 Ｈ Ｉ Ｔ 细胞中调节基因转录的机制,将不同的 Ｃ Ｂ Ｐ片段瞬时转染到细胞中,观察其转录活性．实验表明,在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ 均可诱导 Ｃ Ｂ Ｐ３０（ Ｃ Ｒ Ｅ Ｂ结合功能区）转录活性增强,并有协同效应． Ｐ Ｋ Ｃ对 Ｃ Ｂ Ｐ３０ 的转录活性无影响;与 Ｃ Ｒ Ｅ Ｂ有更强结合力的 Ｃ Ｂ Ｐ Ｋ Ｉ Ｘ Ｓ／ Ｂ（氨基酸序列短于 Ｃ Ｂ Ｐ３０ 的 Ｃ Ｒ Ｅ Ｂ结合功能区）其基本转录活性及膜去极化、ｃ Ａ Ｍ Ｐ诱导下的转录活性均比 Ｃ Ｂ Ｐ３０ 更强．反义 Ｃ Ｒ Ｅ Ｂ 的过度表达可降低 ｃ Ａ Ｍ Ｐ诱导的 Ｃ Ｂ Ｐ的转录活性．提示在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ对共转录因子 Ｃ Ｂ Ｐ转录活性的调节作用通过 Ｃ Ｒ Ｅ Ｂ介导．     

p300/CBP及其相关因子PCAF与转录调控

p300/CBP及相关因子PCAF具有乙酰转移酶活性,能通过乙酰化组蛋白和非组蛋白的方式参与基因的转录调控.同时,它们能在转录因子和基本转录复合物之间起到桥梁作用,而且也能为整合多种转录因子提供支架,是一种典型的转录辅激活子. p300/CBP与细胞周期调控、细胞凋亡以及癌症的发生等过程之间有着直接的联系。本文概括了p300/CBP与PCAF的基本特性,并简要介绍它们与其他蛋白之间的相互作用,特别是E1A的最新研究进展。     

p38在小鼠着床前胚胎中的表达（简报）

探讨p38 MAPK在小鼠着床前胚胎期的表达图式,并对其作用作初步分析。用免疫印迹法分析胚胎全裂解物中的p38蛋白。为考察p38在着床前发育中的作用,在胚胎培养液中添加p38专一性抑制剂SB203580。此外对同位素标记的胚胎作双向电泳分析,示踪ZGA(zygotic gene activation,合子型基因激活)标志物TRC的表达情况。在卵母细胞中能检测到低水平的p38蛋白,而在合子中的检测度更低,表明p38是贮存于卵母细胞内的母型转录物,自减数分裂期随其它母型转录物一起逐步降解。到2细胞中期p38蛋白的表达量开始恢复,在4细胞时达到顶峰,在8细胞时又跌落。D38蛋白在2到4细胞期的表达量上升提示该蛋白在小鼠着床前胚胎发育中可能发挥一定作用。经与p38抑制剂SB203580共培养后的2细胞中期胚胎中仍能清晰检测到TRC,因而以TRC为标志的ZGA对SB203580不敏感。SB203580同样不能阻止胚胎发育到桑椹胚期。