CELL-SPECIFIC TRANSCRIPTION OF THE PERIPHERIN GENE IN NEURONAL CELL-LINES INVOLVES A CIS-ACTING ELEMENT SURROUNDING THE TATA BOX

Peripherin is a neurone-specific intermediate filament protein expressed mostly in the peripheral nervous system. To localize sequences that are important for the regulation of peripherin gene transcription, we have functionally dissected its promoter. Transfection into different cell lines and deletion mapping of peripherin-lacZ hybrid constructs indicated that the first 98 bp preceding the transcription start site of the gene were sufficient to confer cell-type specific expression. DNase I footprinting experiments revealed three protected sequences in this region, that were named PER1, PER2 and PER3. The PER2 and PER3 elements, localized between -98 to -46, interact with proteins that seem widely distributed. Deletion of these elements severely decreased the level of reporter gene activity. The PER1 element, which overlaps the TATA box, interacts with a DNA-binding protein prevailing in peripherin expressing cell lines. However, the core promoter, which contains the PERI element, was inefficient in driving gene expression. Experiments designed to test the contribution of each element showed that PER2 and PER-3 were important in determining the level of expression, while PER1 was important for cell-type specificity. In fact the polyoma virus enhancer linked to the peripherin gene core promoter was found to limit reporter gene activity to peripherin expressing cell lines. Together, these experiments indicate that co-operative interactions between different regions of the promoter are necessary for efficient and cell-type specific transcription of the peripherin gene in a subset of neuronal cells.