Simvastatin induces proliferation inhibition and apoptosis in C6 glioma cells via c-jun N-terminal kinase

The lipid-lowering drugs, statins, induce apoptosis in a variety of tumor cells. Here we investigated the apoptotic effect of the lipophilic statin, simvastatin, in C6 glioma cells and the underlying effects on intracellular signal transduction. Simvastatin inhibited cell proliferation totally after 20 h of treatment as shown by the decrease in proliferating cell nuclear antigen expression in the nucleus. Subsequently, simvastatin caused apoptotic cell death by shrinkage of cytoplasm and condensation of chromatin, and DNA fragmentation. The features of apoptosis were visible only after 48 h of treatment, possibly reflecting a requirement for cell commitment to growth arrest. In immunocytochemical and immunoblotting experiments we have shown that simvastatin markedly increased the phosphorylation of ATF-2 and c-jun in the nucleus of the C6 glioma cells at early time points which was preserved even 24 h after treatment. In contrast, activities of protein kinases Erk1/2 and AKT in the cell survival pathway remained unchanged throughout the treatment. Selective inhibitor of JNK, but not p38 kinase, reduced simvastatin-induced cell death and ATF-2 and c-jun phosphorylation suggesting that JNK-dependent activation of ATF-2 and c-jun may play an important role in simvastatin-induced proliferation inhibition and apoptosis in C6 glioma cells. These observations suggest that statins may have clinical significance in the prevention of glial tumors beyond their cholesterol-lowering effect and JNK may be a rational target for sensitizing glioma cells to chemotherapeutic agents.     

Differences in the interactions of oncogenic adenovirus 12 early region 1A and nononcogenic adenovirus 2 early region 1A with the cellular coactivators p300 and CBP

Association with the cellular coactivators p300 and CBP is required for the growth-regulatory function of adenoviral (Ad) early region 1A (E1A) proteins. E1A regions necessary for these interactions overlap with domains involved in the induction of tumours in immunocompetent rodents through highly oncogenic Ad12. Differences in the association of cellular factors with the respective E1A domains of Ad12 and nononcogenic Ad2 might therefore be involved in serotype-specific oncogenicity. We analyzed the interaction of the Ad12 E1A 235R protein with p300 and CBP. Here we demonstrate that in the case of Ad12, but not Ad2/5, amino acids (aa) 1-29 of E1A proteins are sufficient to bind the p300-C/H3 domain in vivo and wild-type p300 in vitro. The conserved arginine-2, which is essential for the interaction between Ad2 E1A and p300, was dispensable for the Ad12 E1A 235R-p300 interaction in vitro. In addition to the p300-C/H3 region, we identified a second domain within p300 (aa 1999-2200) binding to the 235R protein. Contrary to p300, the amino-terminus and CR1 are necessary to associate with CBP. The aa 1-29 of the 235R protein but not CR1 are essential for the repression of colTRE-driven gene expression. This repression function is strictly dependent on p300 but not on CBP.     

HIV-1感染引起组蛋白乙酰化和增加p21WAF1表达

目的：DNA甲基化和组蛋白乙酰化是基因表达调控的主要形式。人类免疫缺陷病毒（HIV-1）可引起T淋巴细胞DNA甲基化酶上调。本文旨在明确HIV-1对细胞周期依赖刺激酶抑制剂p21^WAF1表达的影响。方法：建立HIV-1感染的Hut78细胞系；以RT-PCR和Westem blotting 分析p21^WAF1表达情况；以亚硫酸氢钠修饰DNA和基因测序，研究p21^WAF1基因启动子甲基化，以Western blot-ting 和染色体免疫测定探究总组蛋白和与p21^WAF1基因启动子相关的组蛋白乙酰化水平。并以GST pull-down和免疫沉淀分析HIV-1导致乙酰化及乙酰化引起p21^WAF1过表达的可能机理。结果：HIV-1感染后，其反式激活蛋白Tat与辅助转录因子P/CAF、hGCN5结合，共同刺激组蛋白H3乙酰化。尽管p21^WAF1启动子部分区域有甲基化发生，但p21^WAF1表达仍上调。这可能与E2A对p21^WAF1的作用有关。结论：HIV-1感染可引起T淋巴细胞p21^WAF1基因的甲基化和乙酰化紊乱，导致p21^WAF1表达增强。