Purification of growth hormone-specific transcription factor GHF-1 containing homeobox.
Pituitary-specific expression of the growth hormone (GH) gene is governed by a transcription factor, GHF-1, that binds to two sites within its promoter. Recently, GHF-1 was shown to be a member of the homeobox family of DNA-binding proteins. An important question is whether GHF-1 controls the expression of other pituitary specific genes, such as prolactin (Prl), expressed in closely related cell types. To this end, GHF-1 was purified from extracts of GH- and Prl-expressing pituitary tumor cells and identified as a 33-kilodalton polypeptide. Although GHF-1 bound to and activated the GH promoter, it did not recognize the Prl promoter. However, at least one other factor in the same extracts, which was easily separated from GHF-1, bound to several sites within the Prl but not the GH promoter. Antibodies to GHF-1 did not react with the Prl binding activity. These results imply that the pituitary-specific expression of GH and Prl is governed by two distinct trans-acting factors.
Castrillo
J L
JL
Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla 92093.
Bodner
M
M
Karin
M
M
D004268:DNA-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D013006:Growth Hormone / Q000235:genetics*; D006801:Humans; D008970:Molecular Weight; D010449:Peptide Mapping; D010902:Pituitary Gland / Q000502:physiology; D011388:Prolactin / Q000235:genetics; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D014157:Transcription Factors; D011388:Prolactin; D013006:Growth Hormone