Isolation and characterization of the chicken vitamin D receptor gene and its promoter

✍ Scribed by Zhongjian Lu; Frederic Jehan; Claudia Zierold; Hector F. DeLuca

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 165 KB
• Volume: 77
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(20000401)77:1<92::aid-jcb10>3.0.co;2-n

✦ Synopsis

The sequences from several independent cDNA clones encoding the chicken vitamin D receptor as well as primer extension assay have clearly delineated the 5Ј terminus and the transcriptional start site. Screening a chicken genomic library produced genomic clones containing vitamin D receptor (VDR) gene fragments. Restriction map of clone 8 showed that the 18.6-kb chicken VDR fragment has exons 1 and 2, intron 1, part of intron 2, and 7-kb 5Ј flanking region. Exons 1, 2 , and 3 found in the chicken VDR gene shares low homology with its mammalian counterparts (i.e., E1A, E1B, and E1C in human). By contrast, the fourth exon and following exons for the coding region of VDR gene are highly conserved between avian and mammalian species. While the fourth exon bears the ATG sites for translation initiation in mammals, the third exon in birds has two extra ATG sites for leaky translation as determined previously. Thus, the avian VDR has more N-terminal sequence than the mammalian VDR and is found in two distinct forms. The 5Ј flanking region from genomic clone 8 shares considerable homology in several regions with the human and mouse VDR promoters. Moreover, the 5Ј flanking region of chicken VDR gene possesses promoter activity, as shown by its ability to drive the luciferase reporter gene in cell transfection assays. Like other steroid receptor promoters, the chicken VDR promoter contains no TATA box but possesses several GC boxes or SP1 sites. A series of deletional promoter constructs established that the proximal GC boxes are the major drivers of gene transcription, while the more upstream sequences have repressive elements.