title: Regulation of the 5'-flanking region of the human CYP27B1 gene in osteoblast cells.
abstract: Synthesis of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is catalysed by the enzyme 25-hydroxyvitamin D(3)-1alpha-hydroxylase (CYP27B1). Regulation of CYP27B1 gene expression is poorly understood, particularly in non-renal tissues including bone where 1,25(OH)(2)D(3) is hypothesised to serve autocrine/paracrine roles. Transient transfection of ROS 17/2.8 osteoblast-like cells with reporter gene constructs containing deletions of the 5'-flanking region of the human CYP27B1 gene revealed a proximal promoter, enhancer region and strong upstream repressive region. Putative CCAAT and GC boxes, as well as Ets protein binding sites were shown to contribute to promoter and enhancer activities respectively in common with kidney and prostate cells. Inhibition of basal expression was largely attributed to a palindrome 5'-GTCTCAGAC-3' (-1015/-1007bp) that contains two putative canonical Smad binding elements. We conclude that repression of CYP27B1 gene expression may be a common event but the novel inhibitory elements we have identified may be unique to osteoblasts.
authors.affiliation: Department of Medicine, Austin Health, University of Melbourne, Australia. atur@unimelb.edu.au
authors.forename: A G
authors.initials: AG
authors.lastname: Turner
authors.forename: P P
authors.initials: PP
authors.lastname: Dwivedi
authors.forename: P H
authors.initials: PH
authors.lastname: Anderson
authors.forename: B K
authors.initials: BK
authors.lastname: May
authors.forename: H A
authors.initials: HA
authors.lastname: Morris
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics*; D024506:5' Flanking Region / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D004252:DNA Mutational Analysis; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D017384:Sequence Deletion; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D016212:Transforming Growth Factor beta; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase