Expression of angiopoietin-2 in endothelial cells is controlled by positive and negative regulatory promoter elements.
OBJECTIVE
Angiopoietin-2 (Ang-2) is a non-signal transducing ligand of the endothelial receptor tyrosine kinase Tie-2. Ang-2 is produced by endothelial cells and acts as an autocrine regulator mediating vascular destabilization by inhibiting Angiopoietin-1-mediated Tie-2 activation. To examine the transcriptional regulation of Ang-2, we studied the Ang-2 promoter in endothelial cells and nonendothelial cells.


RESULTS
The human Ang-2 promoter contains a 585-bp region around the transcriptional start site (-109 to +476) that is sufficient to control endothelial cell-specific and cytokine-dependent Ang-2 expression. Strong repressor elements of Ang-2-promoter activity are located in the 5'-region of the promoter and in the first intron. The Ets family transcription factors Ets-1 and Elf-1 act as strong enhancers of endothelial cell Ang-2-promoter activity. Ets-binding sites -4 and -7 act as positive regulators, whereas Ets-binding site -3 acts as negative regulator. Demethylation experiments revealed that the Ang-2 gene (in contrast to the Tie-2 gene) is not controlled by imprinting.


CONCLUSIONS
The data determine unique positive and negative regulatory mechanisms of endothelial cell Ang-2 expression and provide further evidence for the critical role of Ang-2 as a key autocrine regulator of vascular stability and responsiveness.
Department of Vascular Biology and Angiogenesis Research, Tumor Biology Center, D-79106 Freiburg, Germany.
Anja
A
Hegen
Stefanie
S
Koidl
Karin
K
Weindel
Dieter
D
Marmé
Hellmut G
HG
Augustin
Ulrike
U
Fiedler
D024506:5' Flanking Region / Q000235:genetics; D042702:Angiopoietin-2 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D001011:Aorta / Q000166:cytology; D001483:Base Sequence / Q000235:genetics; D002417:Cattle; D002460:Cell Line; D045744:Cell Line, Tumor; D003001:Cloning, Molecular / Q000379:methods; D016207:Cytokines / Q000502:physiology; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology; D042783:Endothelial Cells / Q000737:chemistry* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000737:chemistry / Q000378:metabolism; D018392:Genomic Imprinting / Q000235:genetics; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000196:embryology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000502:physiology*; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000502:physiology; D050783:Proto-Oncogene Proteins c-ets; D014157:Transcription Factors / Q000502:physiology; D024363:Transcription Initiation Site
D042702:Angiopoietin-2; D016207:Cytokines; D004268:DNA-Binding Proteins; C512897:ELF1 protein, human; C494041:ETS1 protein, human; C512896:Elf1 protein, mouse; C494042:Ets1 protein, mouse; D009687:Nuclear Proteins; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D014157:Transcription Factors; D004247:DNA