Lineage-specific regulation of the vasoactive intestinal peptide gene in neuroblastoma cells is conferred by 5.2 kilobases of 5'-flanking sequence.

AUTOR(ES)

Waschek, J A

RESUMO

The expression of a transfected plasmid containing 5.2 kilobases (kb) of 5' regulatory DNA sequence of the human vasoactive intestinal peptide (VIP) gene attached to coding sequences of the reporter gene chloramphenicol acetyltransferase (CAT) was compared with endogenous VIP expression in subclones of the human neuroblastoma cell line SK-N-SH. These subclones vary widely in basal and inducible quantities of VIP and its precursor mRNA and can be interconverted under specified culture conditions. Endogenous VIP immunoreactivity, detectable in all subclones, was lowest in the neuronal subclone SH-SY-5Y, whereas 15- to 25-fold higher levels were observed in the epithelial-appearing SH-EP and intermediate SH-IN subclones. Treatment with 10 nM phorbol 12-myristate 13-acetate (PMA) stimulated VIP peptide levels approximately 5-fold in SH-SY-5Y cells but did not increase appreciably VIP levels in the other subclones. Treatment with 2.5 microM forskolin resulted in less than 50% stimulation of VIP expression in all subclones. Levels of mRNA encoding the VIP precursor generally paralleled these differences in VIP immunoreactivity. In cells transfected with the VIP/CAT fusion gene, CAT activity reflected closely these differences in basal VIP expression and the changes in response to PMA and forskolin. Deletion of 2.7 kb of the most upstream sequences resulted in an 80-90% reduction in basal CAT activity in SH-IN, but not SH-SY-5Y cells, and resulted in an 80% reduction in PMA stimulation in SH-SY-5Y cells. Deletion to within 74 nucleotides of the transcription start site resulted in CAT expression in SH-IN cells that was only 3% of that seen with the full 5.2-kb flanking sequences and further diminished the remaining PMA responsiveness in SH-SY-5Y cells. The data indicate that important cell-type-specific transcription regulatory sequences reside greater than 2.5 kb upstream from the VIP transcription start site.

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