INTERACTION OF NUCLEAR FACTORS FROM YOUNG AND OLD RAT-BRAIN REGIONS WITH REGULATORY SEQUENCES OF THE D-2 DOPAMINE-RECEPTOR GENE PROMOTER

Alterations in the number or functional state of D-2 dopamine receptor s have been implicated in the decreased motor abilities associated wit h normal aging, Parkinson's disease and other neurodegenerative diseas es. Previous work has demonstrated a substantial decrease in D-2 recep tor-containing neurons, receptor proteins, steady-state mRNA levels, a nd the rate of mRNA synthesis with age in the rat striatum in particul ar and in mammalian brains in general. These observations suggest that one key area of regulatory control is at the level of transcriptional initiation and/or elongation. In the present study gel mobility shift experiments were used to assess the interaction of nuclear proteins f rom different rat brain regions with DNA containing putative DNA regul atory sites of the transcriptionally active rat D-2 receptor gene prom oter. Oligonucleotides containing either of the two SP1 binding sites immediately upstream of the primary transcriptional start site were bo und by proteins found in nuclear extracts obtained from rat striatum, hippocampus, cortex, and cerebellum. Extracts from striatum and hippoc ampus formed predominantly low molecular weight complexes which do not contain SP1, as well as a small amount of high molecular weight compl exes which may contain SP1 or an SP1-related protein. Cerebellar extra cts formed two similar sets of complexes, but they were formed in roug hly equal amounts. Extracts from cortex produced a more involved patte rn of complexes, but still formed both high molecular weight complexes which contain SP1 and low molecular weight complexes which do not con tain SP1. There were differences in the gel mobility as well as the re lative amounts of complexes formed with the two SP1-specific oligonucl eotides among different brain regions. With respect to possible age-re lated changes in transcription of the D-2 dopamine receptor gene, ther e appeared to be no statistically significant difference in the DNA-pr otein complexes formed with striatal nuclear proteins from a populatio n of young rats versus a population of old rats.