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.     

Intranuclear localization of the transcription coadaptor CBP/p300 and the transcription factor RBP-Jk in relation to EBNA-2 and -5 in B lymphocytes

We have studied the expression and the localization of the cellular proteins CBP/p300 and RBP-Jk in in vitro EBV-infected human B lymphocytes in relation to the EBNA-2 and EBNA-5 proteins. We found that the level of CBP/p300 was elevated drastically by EBV infection and also after activation by CD40 ligation. Thus the increase in CBP/p300 expression in the EBV-infected cells is related to the virus-induced activation and proliferation of the cells. EBNA-2 and RBP-Jk colocalized in the nucleoplasm, which is in accordance with their functional interaction. We confirmed earlier reports about the presence and colocalization of EBNA-5 and CBP in the nuclear POD bodies. On the other hand, neither EBNA-2 nor p300 was detected in the PODs. The expression of these two proteins overlapped in some distinct dots of the nucleoplasm. Taken together, the different patterns of CBP and p300 expression and their different localization in relation to the PML bodies and two EBV-encoded proteins in the B cells may provide some clue to their distinct functional roles.     

Salinomycin suppresses TGF-β1-induced EMT by down-regulating MMP-2 and MMP-9 via the AMPK/SIRT1 pathway in non-small cell lung cancer

Salinomycin (Sal) is a recently identified anti-tumor drug for treating several types of solid tumor; however, its effects on the migratory and invasive properties of non-small cell lung cancer (NSCLC) remain unclear. This study investigated the inhibitory effect underlying mechanisms of Salon transforming growth factor-β1 (TGF-β1)-induced epithelial-to-mesenchymal transition (EMT) and cell migration. Sal solidly blocked cell migration and invasion enhancement by TGF-β1-induced EMT, through recovering E-cadherin loss and suppressing mesenchymal markers induction, as well as TGF-β1-mediated AMPK/SIRT signaling activity upregulation. The pharmacologic inhibition or knockdown of AMPK or SIRT1 can act synergistically with Sal to inhibit TGF-β1-induced MMP-2 and MMP-9. In contrast, AMPK or SIRT1 upregulation can protect against TGF-β1-induced MMP-2 and MMP-9 inhibition by Sal. Next we demonstrated that the MMP-2 and MMP-9 knockdown can act synergistically with Sal to inhibit TGF-β1-induced EMT. Moreover, treatment of PMA of MMP activator increased TGF-β1-induced MMP-2 and MMP-9, even with Sal. Our results demonstrate that Sal suppresses TGF-β1-induced EMT by downregulating MMP-2 and MMP-9 through the AMPK/SIRT pathway, thereby inhibiting lung cancer cell migration and invasion.