Rat tenascin-R gene: structure, chromosome location and transcriptional activity of promoter and exon 1

Tenascin-R is an extracellular matrix protein expressed exclusively in the central nervous system where it is thought to play a relevant role in regul ating neurite outgrowth. We have i) cloned the cDNA of the rat tenascin-R 5 ' region; ii) defined its genomic organization, obtaining the sequence of t wo novel untranslated exons; iii) mapped the gene to rat chromosome 13q23 a nd suggested a previously unreported synteny between rat chromosome 13q23, human chromosome 1q24, and mouse chromosome 4E; and iv) sequenced and chara cterized the elements responsible for its neural cell-restricted transcript ion. We found that two discrete regions of the rat gene (the first in the p roximal promoter, the second in the first exon) are independently able to a ctivate to a high degree the transcription of a reporter gene in either hum an or rat neuroblastoma cell lines but not in other cell lines. Based on th is observation, we reevaluated the arrangement of transcriptionally active regions in the human tenascin-R gene we recently cloned and found that the human gene also contains an exon sequence able to initiate and sustain tran scription independently of promoter sequences.