Characterization of a unique enhancer element responsive to cyclic adenosine 3',5'-monophosphate and elevated calcium.
The VL30 family of defective retrovirus-like elements is abundantly transcribed in response to numerous transforming and proliferative stimuli. We have identified a novel enhancer element in the long terminal repeat of the transcriptionally active VL30 element RVL-3. The RVL-3 enhancer mediates a calcium-dependent induction of gene expression in response to treatment with either epidermal growth factor or the phorbol ester tumor promoter 12-O-tetradecanoylphorbol acetate. In this report we present in vivo and in vitro evidence indicating that the RVL-3 enhancer is also responsive to cAMP in the presence of elevated intracellular calcium. Proteins present in nuclear extracts obtained from Rat-1 fibroblasts bind specifically to a 20-basepair sequence within the RVL3 triple repeat. Competition binding studies and mutational analyses indicate that the cAMP responsiveness maps to the same region responsible for mediating the inductive response to epidermal growth factor and 12-O-tetradecanoylphorbol. The responsive sequence is different from previously described enhancer elements. This novel enhancer mediates transcription by multiple agonists and promotes a greater than additive increase in gene expression when more than one signal transduction pathway is stimulated simultaneously.
Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland 97201-3098.
K D
KD
Rodland
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Pribnow
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Lenormand
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SL
Chen
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BE
Magun
D001483:Base Sequence; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology* / Q000502:physiology; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004347:Drug Interactions; D004742:Enhancer Elements, Genetic; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts; D015870:Gene Expression / Q000187:drug effects*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D015398:Signal Transduction; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin
D009687:Nuclear Proteins; D013729:Terpenes; D004815:Epidermal Growth Factor; D019284:Thapsigargin; D004247:DNA; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium