Regulation of Xenopus laevis estrogen receptor gene expression is mediated by an estrogen response element in the protein coding region.
To investigate the 17 beta-estradiol induction of the mRNA coding for the Xenopus laevis estrogen receptor (XER), we cloned the promoter and the 5'-flanking region of the ER gene. Transcription initiation sites were identified by primer extension, and confirmed by the polymerase chain reaction. The promoter and 5'-flanking region contain an imperfect TATA box and a potential CAAT box at -51. Sequence analysis and transfections indicated that no functional estrogen response element (ERE) was present in approximately 3 kb of 5'-flanking region. An imperfect ERE, GGTCAGTTTGACG, which differs from the consensus ERE sequence by 1 nucleotide, was detected in the protein coding region of the gene, approximately 480 nucleotides downstream of the transcription initiation site. In transient transfections using a simple promoter containing two copies of this Xenopus estrogen receptor ERE (XERE), we observed an estrogen-dependent increase in CAT activity of four- to five-fold, to a level approximately 20-fold greater than the activity of the control plasmid lacking the XEREs. In competition gel mobility-shift assays, the XERE exhibited a weak, but clearly detectable, ability to compete for binding of human ER to a labeled consensus ERE. Because it exhibits sequence-specific binding to the ER in competition gel mobility-shift assays, and is able to confer estrogen-dependent transcription on a simple synthetic promoter, the novel XERE, located in the protein coding region of the XER gene appears to represent a weak, but functional, ERE.
Lee
J H
JH
Department of Biochemistry, University of Illinois, Urbana 61801, USA.
Kim
J
J
Shapiro
D J
DJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004967:Estrogens / Q000235:genetics*; D005786:Gene Expression Regulation; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014162:Transfection; D014982:Xenopus laevis / Q000235:genetics*
D004967:Estrogens; D011960:Receptors, Estrogen