Role of the transcription factor C/EBP beta in expression of a rat pregnancy-specific glycoprotein gene.
Pregnancy-specific glycoproteins (PSGs), which are the major placental proteins, and the carcinoembryonic antigens comprise a subfamily within the immunoglobulin superfamily. To understand the molecular mechanisms underlying the control of PSG expression, we characterized the promoter elements of a rodent PSG gene, rnCGM3, and showed that DNA elements at nucleotides -326 to -185 (PI) relative to the translation start site of rnCGM3 function as a promoter. The rnCGM3 PI promoter contains two placental factor binding sites, PISI and PISII. Both are transcription activation elements. In the present report, we screened a placental expression cDNA library with a rnCGM3-PISII probe (nucleotides -263 to -233) encompassing two overlapping palindromes (TGTTGCTCAACATGTTG) and demonstrated that the PISII-binding factor is C/EBP beta, a leucine zipper family of transcription factor. Gel mobility-shift and transient expression analyses showed that C/EBP beta and C/EBP isoforms, C/EBP alpha and C/EBP delta, bind to the PISII element and trans-activate rnCGM3 gene expression. Deletion of PISII from the rnCGM3 PI promoter greatly reduced the basal as well as the C/EBP-activated rnCGM3 expression. Gel supershift assays demonstrated that C/EBP beta is the placental isoform that binds to the PISII site rnCGM3. Moreover, C/EBP beta is expressed in high levels in the placenta, ovary, liver, lung, heart, and spleen, in contrast to C/EBP alpha, which is expressed primarily in the liver and only low levels in the placenta. Our results demonstrate that C/EBP beta is one of the transcription factors that positively regulate rnCGM3 expression during pregnancy.
Chen
H
H
Human Genetics Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Lin
B
B
Chen
C L
CL
Johnson
P F
PF
Chou
J Y
JY
D000818:Animals; D001483:Base Sequence; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics*; D006023:Glycoproteins / Q000235:genetics*; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D009928:Organ Specificity; D010920:Placenta / Q000166:cytology / Q000378:metabolism; D010928:Placental Lactogen / Q000235:genetics; D011257:Pregnancy Proteins / Q000235:genetics*; D011388:Prolactin / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017384:Sequence Deletion; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D022762:CCAAT-Enhancer-Binding Proteins; C497254:Cebpd protein, rat; D004268:DNA-Binding Proteins; D006023:Glycoproteins; D009687:Nuclear Proteins; D011257:Pregnancy Proteins; C089042:Psg19 protein, rat; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D051743:CCAAT-Enhancer-Binding Protein-delta; D011388:Prolactin; D004247:DNA; D010928:Placental Lactogen