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Analysis of regulatory regions in the COL1A1 gene responsible for 1,25‐dihydroxyvitamin D 3 ‐mediated transcriptional repression in osteoblastic cells
Author(s) -
Pavlin Dubravko,
Bedalov Antonio,
Kronenberg Mark S.,
Kream Barbara E.,
Rowe David W.,
Smith Catharine L.,
Pike J. Wesley,
Lichtler Alexander C.
Publication year - 1994
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240560409
Subject(s) - calcitriol receptor , psychological repression , microbiology and biotechnology , gene , osteocalcin , biology , transcriptional regulation , reporter gene , regulatory sequence , regulation of gene expression , transcription factor , gene expression , alkaline phosphatase , biochemistry , enzyme
Abstract The synthesis of type 1 colagen in bone cells is inhibited by the calcium‐regulating hormone 1,25‐dihydroxyvitamin D 3 . Earlier work from our laboratoties has indicated that vitamin D regulation is at the level of transcription, based on result from both nuclear run‐off assays and functional analysis of a hybrid gene consisting of a 3.6 kb COL1A1 promoter fragment fused to the chloraphenicol acetyltransferase reporter gene. In the present study, we investigated the molecular basis for vitamin D‐mediated transcriptional repression of the COL1A1 gene and report the identification of a region within the COL1A1 upstream promoter (the Hindlll‐Pstl restriction fragment between nucleotides‐2295 and ‐1670) which is necessary for 1,25‐dihydroxyvitamin D 3 responsiveness in osteoblastic cells. This hormone‐mediated inhibitory effect on the marker gene parallels the inhibition of the endogenous collagen gene. A 41 bp fragment from this region (between nucleotides‐2256 and ‐2216) contains a sequence which is very similar to vitamin D‐responsive elements identified in the osteocalcin gene. Estracts that binds specifically to this 41 bp fragment, as demonstrated by bandshift anslysis. However, deletion of this vitamin D receptor binding region from either a‐3.5 kb or a‐2.3 kb promoter fragment did not abolish vitamin D responsiveness. These results indicate that a vitamin D response element similar to that described for other D responsive genes (osteocalcin and osteopontin) does not alone mediate the repression of COL1A1 by 1,25‐dihydroxyvitamin D 3 .