IBN 97-28120 McMURRAY Dr. McMurray and colleagues will investigate a novel mechanism by which DNA secondary structure within the control region of the neurotransmitter gene controls both the timing and the level of neurotransmitter synthesis. The control region of the neurotransmitter, proenkephalin, switches between two conformations that control high or low synthesis states. Dr. McMurray and colleagues focus on the mechanism by which switching occurs. Preliminary results suggest that an important transcription factor called CREB stabilizes the high activity state of synthesis and that CREB degradation facilitates switching to the low activity state. Experiments are designed to test this hypothesis. The loss of CREB in proenkephalin A complexes will be monitored after receptor stimulation before and after inhibition of the degrading enzyme. This will establish a role for CREB degradation in control of neurotransmitter synthesis. The proteins bound to each form of the control region will be determined, paying particular attention to the presence of CREB. Finally, we will identify the composition of protein factors that control high and low synthesis. Protein binding and conformation at the mutant enhancers will be correlated with their ability to support either low or high expression. CREB is a major transcription factor that controls memory and adaptation in the brain. Through a degradation mechanism, CREB (with other proteins) appears to control switching and neurotransmitter synthesis. Such a mechanism provides a direct path through a gene control region by which CREB controls the adaptive response of proenkephalin. The switching mechanism allows the economical use of gene control element such that a single site may be utilized in two different ways by the neuron. We believe that such a switch mechanism is a "rapid response" system by which neurotransmitter synthesis can quickly adapt to meet a demand of the cell. A responsive switch that is s ensitive to phosphorylation may represent a novel, but general pathway to assemble efficient transcriptional complexes that optimize the level and timing of neurotransmitter synthesis.
