Molecular Mechanisms of Adaptation
Drugs and stress alter the levels of proteins in brain reward regions by several mechanisms. We have focused primarily on transcriptional mechanisms because adaptations at that level would be expected to be more long-lived than at certain other levels. We examine levels of protein and mRNA expression in the brain with a variety of techniques. We then study control of that gene’s expression in cell culture systems to identify possible promoter elements that might be responsible. Finally, we return to in vivo models where we analyze gene regulation using chromatin immunopreciptation (ChIP) assays, reporter mice, and some of the viral vectors and inducible transgenic systems outlined above. It is clearly a major technical challenge to understand transcriptional mechanisms in the brain in vivo, but we have nonetheless made important progress is this important endeavor.
Along with analysis of gene transcription, we have become interested in recent years in post-transcriptional mechanisms as well, because certain drug- or stress-regulated proteins do not seem to be altered at the transcriptional level. Accordingly, we are analyzing the ability of drugs or stress to modify levels of a protein at the level of RNA splicing, mRNA stability, and protein degradation. This work is in relatively early stages of development, but promises important advances in our understanding of protein regulation in the nervous system.