J. Biol. Chem., Vol. 261, Issue 24, 11064-11070, 08, 1986
Analysis of glucocorticoid unresponsive cell variants using a mouse glucocorticoid receptor complementary DNA clone
JP Northrop, M Danielsen and GM Ringold
We have used a glucocorticoid receptor cDNA isolated from a mouse lymphoma
cell line to characterize receptor mRNA and genomic sequences present in
wild type and mutant rat hepatoma (HTC) and mouse thymoma (S49 and WEHI7)
cells. Wild type rat and mouse cell lines contain two receptor mRNAs, 5 and
7 kilobase pairs (kb) in length, which differ in the length of their
3'-untranslated regions. Levels of receptor mRNA present in mutant HTC,
WEHI7, and S49 cells of the r- (receptorless) phenotype are decreased
compared to wild type cells. This decreased level of receptor mRNA
parallels the decreased level of total immunoreactive receptor protein
found in these cells. S49 nt- (nuclear transfer minus) cells contain
receptor mRNA levels which parallel their hormone binding and
immunoreactive receptor levels. Cells of the r- and nt- phenotype contain
no detectable deletions or rearrangements of the receptor gene. We conclude
that r- cells have lesions which affect the expression of receptor mRNA.
Surprisingly, HTC cells of the r- phenotype differ from WEHI7 and S49 r-
cells in that HTC r- cells contain a lower level of receptor DNA than does
their parental wild type cell line. Although these cells may contain
multiple lesions, it appears that loss of receptor genomic sequences is
responsible, in part, for the phenotype of the HTC r- cells. The S49 nti
(nuclear transfer increase) cells produce glucocorticoid receptors of
molecular weights 40,000 and 94,000. These cells produce, in addition to
the wild type 5- and 7-kb receptor mRNAs, two other receptor messages 5.5
and 3.5 kb in length. RNA blot analysis using various portions of our
receptor cDNA indicates that these are 5' truncated messages and suggests
that the 40-kDa nti receptor is truncated at its NH2-terminal end. These
data also indicate that the hormone and DNA-binding regions of the receptor
are located in the COOH-terminal half of the protein.