It is widely believed that the loss of transforming growth factor-beta- receptors (TGF-beta- R) contributes significantly to carcinogenesis. Functional TGF-beta-R comprise several gene products, including two essential signaling components, the type I TGF-beta-R and the type II TGF-beta-R (TbetaR-II). In several instances in which tumor cells fail to express the TbetaR-II gene at the RNA or protein level, no apparent structural mutations within the coding region of the gene have been observed. This suggests that defects in the promoter region of the TbetaR-II gene and/or in the mechanisms regulating the transcription of the TbetaR-II gene play key roles in its aberrant expression in certain neoplasms. Thus, Dr. Rizzino feels that it is important to understand how the TbetaR-II gene is regulated. Before attempting to understand why this gene is expressed aberrantly in tumor cells, it is important to understand how this gene is regulated normally. Embryonal carcinoma (EC) cells are well suited to achieving this objective, since the differentiation of these cells leads to the turn on of TGF-beta-R. Efforts to understand how the TbetaR-II gene is regulated have shown that differentiation of EC cells leads to the transcriptional activation of this gene. Based on work with the promoter region of the human TbetaR-II gene, two hypotheses have emerged. First, the transcription of the TbetaR-II gene is influenced significantly by at least two positive and two negative regulatory regions. Second, the transcription factor complex NF-Y, which binds to one of the negative regulatory elements in the gene, reduces the transcription of the TbetaR-II gene by interfering with the binding or function of transcription factors that bind to neighboring positive regulatory elements. To test these hypotheses, four Specific Aims are proposed: 1) determine which transcription factors interact with one another to regulate the transcription of the TbetaR-II gene, 2) isolate the promoter region of the murine TbetaR-II gene and map precisely the location of the regulatory elements, 3) identify the transcription factors that bind to the regulatory elements of the TbetaR-II gene, and 4) determine whether differentiation of EC cells alters the chromatin structure of the TbetaR-II gene and the binding of transcription factors to critical regulatory elements. Together, Dr. Rizzino feels that these studies will not only help determine how the TbetaR-II gene is regulated normally, but they will also provide the groundwork for understanding why this gene is aberrantly expressed in tumors.
