Ks. Wang et Rb. Hodgetts, THE ANALYSIS OF REGULATORY SEQUENCES REQUIRED FOR HIGH-LEVEL INDUCTION OF RAT ALPHA(2U)-GLOBULIN GENE-EXPRESSION BY DEXAMETHASONE, Journal of molecular endocrinology, 20(1), 1998, pp. 129-139
The alpha(2u)-globulins are the major urinary proteins in adult male r
ats. They are encoded by a gene family, the expression of which is und
er multihormonal control in the liver. Glucocorticoids are positive re
gulatory hormones and we have analyzed the contribution of 5'-upstream
sequences to the induction by dexamethasone of two cloned members of
the family transfected into mouse L-cells. The results demonstrate tha
t sequences from -762 bp to -226 bp of clone 91 are required for the 2
4-fold level of induction that was observed. Addition of 5.5 kb of ups
tream sequence beyond -762 bp did not alter the level of induction sig
nificantly, whereas deletion of the DNA between -762 bp and -226 bp re
duced inducibility to about 4-fold. Sequencing of this region revealed
that an element, 5'-AGAACAggtTTCAAA-3', similar to the 15 bp consensu
s glucocorticoid response element 5'-AGAACAnnnTGTACC-3', is situated 5
13 bp upstream of the transcription start site. We infer that this ele
ment or its left half site is necessary for the dexamethasone-induced
expression of clone 91 from the observation that a second gene, clone
2, that contained a base substitution at position 5 in the left half s
ite was not inducible. It now appears that at least three distinct cis
-acting regulatory regions, all of which bind to the glucocorticoid re
ceptor in vitro, may contribute to the full induction of clone 91 by d
examethasone. These are: the distal upstream region identified by this
study, a proximal upstream region that binds not only the receptor bu
t also alpha 2uNF1, constitutively expressed nuclear protein required
for induction and a region within the fourth intron that contains five
tandem receptor binding sites.