DIFFERENTIAL CHOLECYSTOKININ BRAIN GUT TRANSCRIPTION INITIATION IN THE RAT - EVIDENCE FOR BRAIN-SPECIFIC START SITES/

Brain/gut cholecystokinin (CCK) has well-established translational and post-translational differences. By contrast, CCK transcription regula tion is reported to be the same in brain and gut, Accordingly, the rat CCK gene has been evaluated for differential brain/gut transcription initiation, Using the 5'-flanking region of the rat CCK gene, DNase I protection assays were performed. We evaluated reporter constructs del eted of the conventional transcription start site in cell culture, Fin ally, brain and gut mRNA was evaluated using both a reverse transcript ion serial primer polymerase chain reaction assay as well as rapid amp lification of cDNA ends (RACE) analysis, TFIID protein protects agains t DNase I digestion between -177 and -196 bp, In tissue culture, spont aneous 5'-flanking region transcription initiation occurs until deleti on proceeds upstream of -140 bp, RACE analysis performed on mRNA from the rat brain identifies heretofore undescribed transcription initiati on at -43 bp 5' as well as at +1,212 (in exon II), These alternative t ranscription initiation sites are utilized in brain, but not gut, The rat CCK gene has alternative 5'-flanking region transcription initiati on sites, These alternative sites are utilized only in the brain, Thes e data may provide insights into how brain and gut respond to their di ffering physiological demands.