Pit-1 binding to specific DNA sites as a monomer or dimer determines gene-specific use of a tyrosine-dependent synergy domain.
Transcriptional activation of the prolactin and growth hormone genes, occurring in a cell-specific fashion, requires short-range synergistic interactions between the pituitary-specific POU domain factor Pit-1 and other transcription factors, particularly nuclear receptors. Unexpectedly, we find that these events involve the gene-specific use of alternative Pit-1 synergy domains. Synergistic activation of the prolactin gene by Pit-1 and the estrogen receptor requires a Pit-1 amino-terminal 25-amino-acid domain that is not required for analogous synergistic activation of the growth hormone promoter. The action of this Pit-1 synergy domain is dependent on the presence of two of three tyrosine residues spaced by 6 amino acids and can be replaced by a comparable tyrosine-dependent trans-activation domain of an unrelated transcription factor (hLEF). The gene-specific utilization of this tyrosine-dependent synergy domain is conferred by specific Pit-1 DNA-binding sites that determine whether Pit-1 binds as a monomer or a dimer. Thus, the critical DNA site in the prolactin enhancer, where this domain is required, binds Pit-1 as a monomer, whereas the Pit-1 sites in the growth hormone gene, which do not utilize this synergy domain, bind Pit-1 as a dimer. The finding that the sequence of specific DNA sites dictates alternative Pit-1 synergy domain utilization based on monomeric or dimeric binding suggests an additional regulatory strategy for differential target gene activation in distinct cell types.
Holloway
J M
JM
Howard Hughes Medical Institute, University of California, San Diego, La Jolla 90293-0648, USA.
Szeto
D P
DP
Scully
K M
KM
Glass
C K
CK
Rosenfeld
M G
MG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002522:Chlorocebus aethiops; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000096:biosynthesis*; D007668:Kidney; D008156:Luciferases / Q000096:biosynthesis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D011388:Prolactin / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine
D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; C494186:Pou1f1 protein, rat; D011994:Recombinant Proteins; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D014443:Tyrosine; D011388:Prolactin; D013006:Growth Hormone; D004247:DNA; D008156:Luciferases