A Y-box protein is a suppressor factor that decreases thyrotropin receptor gene expression.
The decanucleotides in a tandem repeat, -162 to -140 bp, are suppressor elements that decrease TSH receptor (TSHR) gene expression by different mechanisms. A factor(s) interacting with the 3'-decanucleotide compete for proteins that bind the cAMP response element, -139 to -132 bp, a constitutive enhancer necessary for efficient TSHR expression. The 5'-decanucleotide is in a CT-rich, S1 nuclease-sensitive region of the promoter; its suppressor activity has been related to its ability to bind a nonthyroid-specific protein to its coding strand. In this report we clone a complementary DNA encoding a single strand DNA-binding protein that forms a specific protein-DNA complex with the coding strand of the 5'- but not the 3'-decanucleotide and not with the 5'-decanucleotide noncoding or double strand. We show, by cotransfection with TSHR promoter-chloramphenicol acetyltransferase chimeras, that the protein is a suppressor that regulates the function of the 5'- but not the 3'-decanucleotide. The protein is a Y-box protein that was previously cloned as an enhancer factor from the rat liver; it is, however, 95% identical to human YB-1, which suppresses major histocompatibility class II gene expression, and to human nuclease-sensitive element protein-1, a Y-box protein identified by its ability to bind single strand, CT-rich, nuclease-sensitive elements of genes that, like the TSHR, have GC-rich promoters. Unexpectedly, the Y-box protein binds two other sites in the minimal TSHR promoter in a single strand-specific fashion and acts a suppressor at each of these sites. One is associated with the insulin response element of the minimal TSHR promoter and is not in an overtly CT-rich region. The other is located 3' to the cAMP response element in a region termed the S-box, -120 to -113 bp, because of its homology to the S-box of the major histocompatibility class II promoter; this site is in a CT-rich area and, as in the class II promoter, is linked to cAMP-induced gene suppression. A conserved CCTC sequence in each site is important for the binding and suppressor function of the Y-box protein.
Ohmori
M
M
Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Shimura
H
H
Shimura
Y
Y
Kohn
L D
LD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D018076:DNA, Complementary / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D051381:Rats; D011989:Receptors, Thyrotropin / Q000235:genetics*; D013489:Suppression, Genetic; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000494:pharmacology; D014157:Transcription Factors; D014162:Transfection; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D011989:Receptors, Thyrotropin; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D013972:Thyrotropin; D004247:DNA