T. Okazaki et al., A REDOX FACTOR PROTEIN, REF1, IS INVOLVED IN NEGATIVE GENE-REGULATIONBY EXTRACELLULAR CALCIUM, The Journal of biological chemistry, 269(45), 1994, pp. 27855-27862
A rise in extracellular calcium (Ca-e(2+)) suppresses not only secreti
on of parathyroid hormone (PTH) but also expression of the PTH gene to
ensure constant plasma Ca2+ level. A nuclear protein(s) in a wide var
iety of cells bound to the specific DNA elements (negative Ca2+ respon
sive elements, nCaREs) in the human PTH gene in sequence-specific and
Ca(2+)e concentration-dependent manners. Our Southwestern cloning reve
aled that a redox factor protein (ref1), which was known to activate s
everal transcription factors via alterations of their redox state, bel
onged to an nCaRE binding protein. The level of ref1 mRNA as well as o
f its protein was elevated by an increase in Ca-e(2+) concentration. I
n gel shift assay, anti-ref1 antibody eliminated formation of the nCaR
E-protein complex. We also found that there was another protein(s) int
eracting with nCaREs and ref1. Further, experiments with an antisense-
ref cDNA expression vector introduced into cultured cells suggested th
at DNA (nCaRE)-ref1 interaction led to Ca-e(2+)-mediated transcription
al suppression. Thus, it is concluded that ref1 possesses transcriptio
n repressor activity in addition to its function as a transcriptional
auxiliary protein.