The role of the ras/ets signaling pathway in inflammation and tumorigenesis.

Mutation in one of the three ras genes is observed in 30 percent of all human tumors and leukemia and are particularly frequent in pancreatic cancer (90%), colon cancer (50%), and acute myeloid leukemia (30%). Substantial gains in our understanding of ras action at the molecular level have been made in the past decade. However, these significant gains remain far outweighed by what we don't know about ras action. How can one gene family effect such a myriad of basic cell processes in often opposing ways? At least part of the solution to this puzzle lies in realizing that signaling cascades are not linear, but rather a network of interactions. Understanding crosstalk within this network will be key to defining the specificity of ras action in a particular cell type. The long-term goal of this project is to gain a detailed understanding of how specificity is achieved when signals are transmitted by ras from the cell surface to the nucleus. We have identified ets-1 and ets-2 as ras targets in the nucleus that can persistently activate gene expression, and more recently have demonstrated that ets-2 can also repress gene expression in a signaling-dependent fashion.

Ets-2 interacts with the C-terminal domain of Brg-1 in a phosphorylation dependent manner.   Left: A pulldown experiment using GST-Brg1 and 6X-his tagged ets-2 pointed domain (aa 67-170).  The ets-2 pointed domain was labeled with 32-P-ATP by erk-2 in vitro so that only a trace amount (~1%) was labeled.   The figure shows that GST-Brg-1 interacts with unphosphorylated ets-2 (bottom panel, a western using an anti-his-tag antibody), but not with the phosphorylated, radioactive portion of ets-2 (top panel, autoradiogram of the gel, <5% of input radioactivity "pulled down").   GST alone does not bind to ets-2 (as indicated). See Baker et al for details.

The current aims of our research are: 1) To characterize the biochemical interactions of ets-2 with nuclear proteins that are constituents of chromatin modifying complexes; 2) To study the mechanism by which the ets-2-Brg-1 and ets-2 BS69 complexes modulate target gene expression. 3) To study the role of ets-2 in vivo in macrophage function and survival using conditional knockout and knockin mice. A combination of biochemical, molecular, and genetic approaches will be used to gain a more detailed understanding of these processes. A landmark in cancer chemotherapy is the development of drugs that target the action of specific genes, instead of non-specific properties of tumor cells. A more detailed understanding of ras action at the molecular level should allow the development of more and better ways to selectively inhibit tumor-specific functions of this gene family without affecting their key developmental and physiological actions.