The human calbindin-D9k gene. Complete structure and implications on steroid hormone regulation.
Level 5 - mechanism / opinion, no new human data
In vitro molecular biology and biochemical study (no clinical human subjects).
PubMed 8308886 · doi:10.1006/jmbi.1994.1076
What was done
Researchers cloned and sequenced the full human calbindin-D9k gene, characterizing its promoter and 1,300 base pairs of the 5' flanking region. They analyzed potential regulatory motifs (including vitamin D and estrogen response elements) and tested whether the putative human estrogen response element could bind the estrogen receptor using an in vitro gel retardation assay.
What was found
The gene spans approximately 5.5 kilobases on the X-chromosome, contains three exons, and harbors four Alu repeats. A sequence related to a vitamin D response element was identified about 1.1 kilobases upstream of the promoter. A sequence located 50 nucleotides downstream of the promoter shared homology with the rat estrogen response element but had two essential nucleotide changes. In gel retardation assays, the human sequence failed to bind the estrogen receptor.
Why it matters
This study establishes the primary structure of human calbindin-D9k and offers a molecular explanation for species differences in steroid regulation, particularly why estrogen does not induce this gene in human uterus or placenta as it does in rodents.
Limits
The study is entirely in vitro and descriptive. The abstract does not quantify binding kinetics or provide direct in vivo functional expression data from human tissue samples, leaving the proposed link to uterine and placental expression as an inference.
Cited by
- supports Nuclear steroid hormones such as estrogen, testosterone, and active vitamin D bind receptors that enter the cell nucleus to recognize response elements like EREs and VDREs and regulate gene expression.