DNA sequences containing the 5′ flanking region of the rat somatoscatin gene were linked to the coding sequence of the bacterial chloramphenicol acetyl transferase gene. This recombinant plasmid is active in expressing CAT activity in the neuronally derived, somatostatin producing CA-77 cell line. Deletion analyses of the somatostatin promoter show that the sequences proximal to position -60, relative to the cap site are required for expression of this promoter. A 4 base pair deletion of residues -46 through -43 within the somatostatin promoter results in a down mutation in vivosuggesting the existence of an element critical for the expression of the promoter in CA-77 cells. In addition, the somatostatin recombinant and its 5′ deletion constructs preferentially express CAT activity in CA-77 cells, whereas only basal level of expression is observed in HeLa, BSC4O, and RIN-5F cell lines, pointing to the cell specific nature of this promoter.
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