The Pit-1 homeodomain and beta-domain interact with Ets-1 and modulate synergistic activation of the rat prolactin promoter.
Pit-1/GHF-1 is a pituitary-specific, POU homeodomain transcription factor required for development of somatotroph, lactotroph, and thyrotroph cell lineages and regulation of the temporal and spatial expression of the growth hormone, prolactin (PRL), and thyrotropin-beta genes. Synergistic interaction of Pit-1 with a member of the Ets family of transcription factors, Ets-1, has been shown to be an important mechanism regulating basal and Ras-induced lactotroph-specific rat (r) PRL promoter activity. Pit-1beta/GHF-2, an alternatively spliced isoform containing a 26-amino acid insert (beta-domain) within its transcription-activation domain, physically interacts with Ets-1 but fails to synergize. By using a series of Pit-1 internal-deletion constructs in a transient transfection protocol to reconstitute rPRL promoter activity in HeLa cells, we have determined that the functional and physical interaction of Pit-1 and Ets-1 is mediated via the POU homeodomain, which is common to both Pit-1 and Pit-1beta. Although the Pit-1 homeodomain is both necessary and sufficient for direct binding to Ets-1 in a DNA-independent manner, an additional interaction surface was mapped to the beta-domain, specific to the Pit-1beta isoform. Thus, the unique transcriptional properties of Pit-1 and Pit-1beta on the rPRL promoter may be due to the formation of functionally distinct complexes of these two Pit-1 isoforms with Ets-1.
Bradford
A P
AP
Department of Obstetrics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. Andy.Bradford@uchsc.edu
Brodsky
K S
KS
Diamond
S E
SE
Kuhn
L C
LC
Liu
Y
Y
Gutierrez-Hartmann
A
A
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011388:Prolactin / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D051381:Rats; D015398:Signal Transduction / Q000235:genetics*; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; C494041:ETS1 protein, human; C494043:Ets1 protein, rat; D018398:Homeodomain Proteins; C494187:POU1F1 protein, human; C494186:Pou1f1 protein, rat; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D011388:Prolactin