This study focuses primarily on the transcriptional regulation of the G-protein alpha i2 subunit and potential feedback mechanisms by which G proteins are themselves regulated. Transient co- transfection assays demonstrate changes in transcription of several different promoter-reporter genes when introduced into cells with increasing amounts of plasmids directing the synthesis of specific G protein subunits. The combination of this co-transfection assay with in vitro mutagenesis of alpha i2 promoter regions will aid characterization and mapping of regions required for G protein dependent responses. Such studies will permit the association of new functions with specific G protein subunits and the distinction between mechanisms affected by closely realted subunits. GTP-binding (G) proteins are membrane-associated proteins that have critical roles in regulating cellular responses to a variety of external stimuli. G protein-mediated cascades include the generation of cyclic AMP, activation of protein kinase C, and the regulation of several ion channels. These pathways impinge upon other processes that ultimately can affect the functioning of transcription factors and the expression of numerous genes, including G proteins. Multiple control mechanisms appear to be operative in determining tissue specific aqnd differentiation- dependent expression of G proteins. In addition, analysis of DNA sequences from some of these genes reveals potential cAMP and phorbol ester responsive elements near the transcriptional control signals. Knowledge of how G protein pathways interact to influence transcription will lead to a greater understanding of how signal transduction mechanisms coordinate gene expression during cell growth and development.
