Role of TFII-I in signal transduction by growth factors

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TFII-I has recently emerged as an important component of the signal transduction pathways that lead to the c-fos promoter. Though TFII-I was initially identified as a factor that can bind to promoter initiator elements, it is now clear that it also plays a direct role in signal transduction. In lymphocytes, it has been found to be associated with the cytoplasmic BTK tyrosine kinase and is phosphorylated by it. Hemizygousity for TFII-I is closely linked to the neurodevelopmental disorder Williams-Beuren syndrome (WBS) in humans. We have shown that TFII-I binds to upstream regulatory elements of the c-fos promoter and forms in vivo complexes with the serum response factor (SRF) and the STAT family proteins. Overexpression of TFII-I enhances c-fos promoter activation and dominant negative TFII-I inhibits c-fos promoter activation. We have found that the tyrosine phosphorylation of TFII-I is regulated by serum growth factors and that the JAK2 kinase is important for this regulation. In addition, we have found that TFII-I is also regulated by the RhoA and MAP kinase pathways and associates directly with ERK and p38 through its D domain. These findings suggest that TFII-I is a key transcriptional mediator in the serum/RhoA/SRF pathway for immediate early gene expression. In this proposal, we will investigate the role of TFII-I in signal transduction to the nucleus. We will identify critical phosphorylation sites in the protein and will determine the pathways which regulate phosphorylation of TFII-I on both serine threonine and tyrosine. We will then determine the role of these phosphorylation sites in TFII-I activity including DNA binding, protein binding, transactivation, and nuclear translocation. Moreover, we will generate mutations in TFII-I and its associated factors that will disassociate these interactions and allow us to assess the role of TFII-I interactions with serum response factor and MAP kinases in its function. We will also evaluate the possible role of TFII-I as a signaling intermediate in the RhoA- SRF pathway. The results of these studies will help to elucidate and understand an important new signal transduction molecule which may be involved in human disease. Spec. Aims Specific Aim number 1: To map the Phosphorylation sites in TFII-I and analyze the role of Phosphorylation in TFII-I function. Specific Aim number 2: To determine the role of specific protein interactions in TFII-I function. Specific Aim number 3: To determine the role of MAP kinase and RhoA signaling pathways in TFII-I regulation. Specific Aim number 4: To determine the mechanism of regulation of TFII-I by of JAK kinases. Specific Aim number 5: To determine whether TFII-I is required for the induction of endogenous c-fos gene.