OBJECTIVE: To determine the mechanism by which expression of the murine ABCA1 gene is highly induced by cAMP analogues. METHODS AND RESULTS: ABCA1 mRNA turnover cannot account for its induction by cAMP. Thus cAMP induction of ABCA1 mRNA occurs at a transcriptional level. Shotgun cloning DNA fragments from the murine ABCA1 locus identified a strong cAMP responsive enhancer located in the first intron, which led to 25- to 100-fold cAMP-mediated induction of reporter gene activity. Deletions and mutations of this enhancer led to the identification a cAMP-responsive element (CRE) that was essential for the cAMP induction. Furthermore, the capacity of this CRE site to mediate the cAMP induction required the presence of a STAT3/4 element located 81 bp away. A dominant-negative CREB expression vector inhibited the cAMP induction of ABCA1, demonstrating that CREB was required for cAMP induction of ABCA1 expression in RAW264.7 cells. CONCLUSIONS: Phospho-CREB1 controls the cAMP-mediated induction of murine ABCA1 gene expression through a CRE site acting in cooperation with a nearby STAT element. This CRE site is not conserved in the human ABCA1 gene, explaining why human ABCA1 is not strongly stimulated by cAMP analogs.
OBJECTIVE: To determine the mechanism by which expression of the murineABCA1 gene is highly induced by cAMP analogues. METHODS AND RESULTS:ABCA1 mRNA turnover cannot account for its induction by cAMP. Thus cAMP induction of ABCA1 mRNA occurs at a transcriptional level. Shotgun cloning DNA fragments from the murineABCA1 locus identified a strong cAMP responsive enhancer located in the first intron, which led to 25- to 100-fold cAMP-mediated induction of reporter gene activity. Deletions and mutations of this enhancer led to the identification a cAMP-responsive element (CRE) that was essential for the cAMP induction. Furthermore, the capacity of this CRE site to mediate the cAMP induction required the presence of a STAT3/4 element located 81 bp away. A dominant-negative CREB expression vector inhibited the cAMP induction of ABCA1, demonstrating that CREB was required for cAMP induction of ABCA1 expression in RAW264.7 cells. CONCLUSIONS: Phospho-CREB1 controls the cAMP-mediated induction of murineABCA1 gene expression through a CRE site acting in cooperation with a nearby STAT element. This CRE site is not conserved in the humanABCA1 gene, explaining why humanABCA1 is not strongly stimulated by cAMP analogs.
Authors: Eric Frisdal; Philippe Lesnik; Maryline Olivier; Paul Robillard; M John Chapman; Thierry Huby; Maryse Guerin; Wilfried Le Goff Journal: J Biol Chem Date: 2011-07-08 Impact factor: 5.157
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