Regulation of mouse Slo gene expression: multiple promoters, transcription start sites, and genomic action of estrogen.
The large conductance, voltage- and Ca(2+)-activated K(+) channel plays key roles in diverse body functions influenced by estrogen, including smooth muscle and neural activities. In mouse (m), estrogen up-regulates the transcript levels of its pore-forming alpha-subunit (Slo, KCNMA1), yet the underlying genomic mechanism(s) is (are) unknown. We first mapped the promoters and regulatory motifs within the mSlo 5'-flanking sequence to subsequently identify genomic regions and mechanisms required for estrogen regulation. mSlo gene has at least two TATA-less promoters with distinct potencies that may direct mSlo transcription from multiple transcription start sites. These qualities mark mSlo as a prototype gene with promoter plasticity capable of generating multiple mRNAs and the potential to adapt to organismal needs. mSlo promoters contain multiple estrogen-responsive sequences, e.g. two quasi-perfect estrogen-responsive elements, ERE1 and ERE2, and Sp1 sites. Accordingly, mSlo promoter activity was highly enhanced by estrogen and blocked by estrogen antagonist ICI 182,780. When promoters are embedded in a 4.91-kb backbone, estrogen responsiveness involves a classical genomic mechanism, via ERE1 and ERE2, that may be complemented by Sp factors, particularly Sp1. Simultaneous but not individual ERE1 and ERE2 mutations caused significant loss of estrogen action. ERE2, which is closer to the proximal promoter, up-regulates this promoter via a classical genomic mechanism. ERE2 strategic position together with ERE1 and ERE2 independence and Sp contribution should ensure mSlo estrogen responsiveness. Thus, the mSlo gene seems to have uniquely evolved to warrant estrogen regulation. Estrogen-mediated mSlo genomic regulation has important implications on long term estrogenic effects affecting smooth muscle and neural functions.
Kundu
Pallob
P
Department of Anesthesiology, Division of Molecular Medicine, the. Electronic address: pallob@ucla.edu.
Alioua
Abderrahmane
A
Department of Anesthesiology, Division of Molecular Medicine, the.
Stefani
Enrico
E
Department of Anesthesiology, Division of Molecular Medicine, the; Department of Physiology, UCLA, Los Angeles, California 90095; Cardiovascular Research Laboratories and Brain Research Institute, UCLA, Los Angeles, California 90095.
Toro
Ligia
L
Department of Anesthesiology, Division of Molecular Medicine, the; Cardiovascular Research Laboratories and Brain Research Institute, UCLA, Los Angeles, California 90095; Department of Molecular and Medical Pharmacology and UCLA, Los Angeles, California 90095.
D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D004967:Estrogens / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic; D020218:Response Elements; D024363:Transcription Initiation Site
D004967:Estrogens; C494841:KCNMA1 protein, human; C465449:Kcnma1 protein, mouse; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits