The E-cadherin promoter: functional analysis of a G.C-rich region and an epithelial cell-specific palindromic regulatory element.
The cell-cell adhesion molecule E-cadherin is specifically expressed in epithelia and is involved in the maintenance of the epithelial phenotype. Expression of E-cadherin is downregulated in many poorly differentiated carcinomas, which leads to higher motility and invasiveness of the cells. To examine the mechanisms that regulate tissue-specific expression, we have characterized the promoter of the E-cadherin gene. We found that an upstream fragment (positions -178 to +92) mediates strong expression of a chloramphenicol acetyltransferase reporter gene in epithelial cells (i.e., 60% of the level obtained with simian virus 40 promoter/enhancer constructs), whereas in nonepithelial cells this promoter was either inactive or much less active. By DNase I footprinting and gel retardation analysis as well as through functional dissection of the regulatory sequences, we identified two regions that contribute to tissue-specific activity of the promoter: (i) a G-C-rich region between -25 and -58 that generates basic epithelial promoter activity, most likely in combination with an "initiator" element present at the single transcription start site of the gene, and (ii) a palindromic sequence between -75 and -86 (named E-pal) that potentiates the activity of the proximal E-cadherin promoter and confers epithelial cell-specific activity on a simian virus 40 promoter. The E-pal sequence is homologous to cis regulatory elements active in keratin gene promoters and competes with these elements for nuclear factor binding. Interestingly, the activity of the E-cadherin promoter was reduced in dedifferentiated breast carcinoma cells, indicating that the identified elements are subject to negative regulation during tumor progression.
Behrens
J
J
Institute of Cell Biology (Tumor Research), University of Essen Medical School, Federal Republic of Germany.
Löwrick
O
O
Klein-Hitpass
L
L
Birchmeier
W
W
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015820:Cadherins / Q000235:genetics*; D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology; D003850:Deoxyribonuclease I; D004848:Epithelium / Q000502:physiology; D015698:Genomic Library; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic
D015820:Cadherins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D003850:Deoxyribonuclease I