The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas. The present work demonstrates that MUC1 associates with the p53 tumor suppressor, and that this interaction is increased by genotoxic stress. The MUC1 cytoplasmic domain binds directly to p53 regulatory domain. Chromatin immunoprecipitation assays demonstrate that MUC1 coprecipitates with p53 on the p53-responsive elements of the p21 gene promoter and coactivates p21 gene transcription. Conversely, MUC1 attenuates activation of Bax transcription. In concert with these results, MUC1 promotes selection of the p53-dependent growth arrest response and suppresses the p53-dependent apoptotic response to DNA damage. These findings indicate that MUC1 regulates p53-responsive genes and thereby cell fate in the genotoxic stress response.

The MUC1 protein is aberrantly overexpressed by most human breast carcinomas. We report that the MUC1 C-terminal subunit associates with estrogen receptor alpha (ERalpha) and that this interaction is stimulated by 17beta-estradiol (E2). MUC1 binds directly to the ERalpha DNA binding domain and stabilizes ERalpha by blocking its ubiquitination and degradation. Chromatin immunoprecipitation assays further demonstrate that MUC1 (1) associates with ERalpha complexes on estrogen-responsive promoters, (2) enhances ERalpha promoter occupancy, and (3) increases recruitment of the p160 coactivators SRC-1 and GRIP1. In concert with these results, we show that MUC1 stimulates ERalpha-mediated transcription and contributes to E2-mediated growth and survival of breast cancer cells. These findings provide evidence that MUC1 stabilizes ERalpha and that this oncoprotein is of importance to the activation of ERalpha function.

A group of pyrene-containing poly(phenylacetylene)s (PPAs) with high molecular weight (M w up to ∼170 000) were synthesized in high yields (up to ∼96%). Simply mixing the polymers and multiwalled carbon nanotubes (MWNTs) in an appropriate solvent afforded the polymer/MWNT hybrids with MWNT contents up to ∼25 wt %, which are soluble in common organic solvents such as chloroform and THF. The solubility can be as high as 637.5 mg/L in THF, thanks to the "additive effect" of the PPA skeleton and the pyrene pendants in solubilizing the MWNTs. The solubilization is realized through the spontaneous wrapping of the polymer chains round the MWNT shells, which is driving by the favorable π-π interactions of the PPA skeleton and the pyrene rings with the MWNT walls. The P2(5)/MWNT hybrid is thermally stable, losing little of its weight when heated to 338 °C. The P2(m)/MWNT hybrids are electronically more conjugated and emit blue-green light more efficiently than their parent polymers upon photoexcitation. The surface photovoltaic cell fabricated from the P2(5)/MWNT hybrid is bipolar, suggesting an efficient photoinduced charge transfer between the two components, i.e., P2(5) and MWNT.