Regulation of gene expression by the CUP27B1 promoter: study of a transgenic mouse model

The enzyme 25-hydroxyvitamin D I -hydroxylase (CYP27B1) is the rate limiting enzyme in the two-step activation process of Vitamin D to its active form 1,25-dihydroxyvitamin D (1,25D) and is located in the mitochondrial fraction of the proximal tubular cells of the kidney. More recently CYP27B 1 activity and expression have also been identified in a number of non-renal cells, which is suggestive of new, previously unidentified roles for Vitamin D in the human body. Although the regulation of CYP27B 1 activity and expression has been a major focus of interest over the past decades, the exact molecular mechanism behind the regulation of CYP27B 1 activity and expression and the role of the CYP27B 1 promoter, herein, are still poorly understood. In this study, we created a transgenic mouse model that expresses the luciferase reporter gene under the control of the full-length, 1.5 kb, human CYP27B I promoter. This animal model allows us to study in vivo the tissue-specific, CYP27B 1 promoter-controlled, regulation of the expression of the CYP27B 1 gene.