Characterization of a single strong tissue-specific enhancer downstream from the three human genes encoding placental lactogen.
The human genes coding for growth hormone (hGH) and placental lactogen (choriosomatomammotropic hormone [hCS]) are clustered on chromosome 17 in the following order: 5' hGH-N hCS-L hCS-A hGH-V hCS-B 3'. So far, a single placenta-specific enhancer has been identified in the locus, 2 kb downstream from the hCS-B gene, and shown to comprise one in vitro binding site for a nuclear protein. We here provide evidence that the hCS-B enhancer is more complex: (i) protection against DNase I digestion in the 3' flanking region of the hCS-B gene reveals four binding sites (DF-1, DF-2, DF-3, and DF-4) for nuclear proteins from either placental or HeLa cells, and (ii) placenta-specific enhancer activity can be fully exerted in transient expression experiments by a 126-bp fragment comprising the DF-3 and DF-4 protein-binding sites. By dissecting this region, we show that enhancer activity is mediated by a synergy between DF-3 and DF-4. Competitions with various oligonucleotides in footprinting and gel retardation experiments indicate that the same protein or set of proteins, different in HeLa and placenta cell nuclei, interacts with sites DF-2, DF-3, and DF-4. We also studied the regions of the hCS-L and hCS-A genes which are highly similar to the hCS-B enhancer. Although they each present the same four protein-binding sites, they exhibit only minor enhancer activity.
Jacquemin
P
P
Laboratoire de Biologie Moléculaire et de Génie Génétique, Université de Liège, Sart Tilman, Belgium.
Oury
C
C
Peers
B
B
Morin
A
A
Belayew
A
A
Martial
J A
JA
D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005260:Female; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins; D010920:Placenta / Q000378:metabolism; D010928:Placental Lactogen / Q000235:genetics*; D011247:Pregnancy; D011485:Protein Binding; D012689:Sequence Homology, Nucleic Acid; D000091262:TEA Domain Transcription Factors; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D000091262:TEA Domain Transcription Factors; C057182:TEAD1 protein, human; D014157:Transcription Factors; D013006:Growth Hormone; D004247:DNA; D010928:Placental Lactogen