Cloning and characterization of the 5'-flanking region of the rat neuron-specific Class III beta-tubulin gene.

The promoter regions of several neuron-specific structural proteins (e.g. neurofilaments, peripherin, Talpha1-tubulin) have revealed potential regulatory elements that could contribute to the choice of a neuronal phenotype during development. We initiated study of the 5'-flanking region of the rat Class III neuron-specific beta-tubulin gene (betaIII-tubulin) because this gene is expressed at the time of terminal mitosis only in neurons and thus its promoter should be an excellent tool for studying neuron-specific gene expression during the transition from proliferative progenitor cell to early neuronal differentiation. We identified the minimal promoter region needed to drive expression of the betaIII-tubulin gene. This minimal region contains multiple putative binding sites for the transcription factors SP1 and AP2, as well as a central nervous system enhancer regulatory element and an E-box. A primer extension analysis identifies a single transcription start site. We highlight several putative regulatory elements that may modulate the expression of the betaIII-tubulin gene in a stage- and tissue-specific manner. In addition, we show that the first 490 bp of the promoter are sufficient to regulate betaIII-tubulin gene expression during neuronal differentiation of PCC7 cells.