Distribution of mRNA encoding Tat-binding protein-1 (TBP-1), a component of 26S proteasome, in the rat brain.

Cellular localization of Tat-binding protein-1 (TBP-1) mRNA is studied in the rat central nervous system (CNS) by in situ hybridization histochemistry. TBP-1 is one of the molecules which interact with HIV Tat and influence HIV amplification. Also, TBP-1 is recognized as a component of a 19S regulatory subunit of the 26S proteasome which degrades ubiquitinated proteins and is essential for a remarkably wide range of cellular processes, including vesicle fusion, proteolysis, peroxisomal and mitochondrial biogenesis and transcription. A detectable amount of TBP-1 mRNA exists widely in neurons but with high heterogeneity in the CNS. Many motor neurons, e.g. those in the oculomotor nucleus, trochlear nucleus, motor trigeminal nucleus, facial nucleus and hypoglossal nucleus, are TBP-1 mRNA positive. In addition, neurons in the sensory nuclei, such as the mesencephalic trigeminal nucleus and the nucleus ambiguus, and many cortical neurons are TBP-1 mRNA positive. These results suggest that TBP-1 is one of the basic molecules in the brain and that the expression of TBP-1 mRNA is differentially regulated at the cellular level, probably reflecting the rate of protein turnover as a whole.