Cyclic AMP-dependent protein kinase (cAPK) modulates synaptic transmission and influences memory and learning. Among the various isoforms of regulatory and catalytic subunits that comprise mammalian cAPK, only the regulatory type I beta (RI beta) subunit is unique to nervous tissue. The requirement for RI beta in neurons is presently unknown. Previous studies demonstrate that holoenzyme containing RI beta activates at lower concentrations of cAMP compared to other forms of cAPK. Thus, neurons that induce RI beta expression may become more sensitive to subsequent hormonal signals and maintain more long-term phosphorylation events. To further elucidate the function of this novel protein, we have begun to investigate its gene. Here we report the isolation of the mouse RI beta promoter as determined by S1 nuclease analysis and transgenic mouse expression. A beta-galactosidase fusion gene containing 1.5 kilobases of 5'-nontranscribed RI beta DNA and 2 kilobases of intron 1 was expressed preferentially in the cortex and hippocampus of the brain and within the spinal cord. In addition to mimicking the location of endogenous RI beta expression, the transgene was activated at a similar time (embryonic day 11.5) during mouse fetal development. Isolation of the RI beta promoter will help identify the elements that direct transcription in a subset of neurons and illuminate the physiological conditions that may regulate RI beta expression. This promoter can also be used to target the expression of wild type and mutant cAPK subunit genes in order to investigate synaptic plasticity in animals.