Angiopoietin-2 is a direct transcriptional target of TAL1, LYL1 and LMO2 in endothelial cells.
The two related basic helix-loop-helix, TAL1 and LYL1, and their cofactor LIM-only-2 protein (LMO2) are present in blood and endothelial cells. While their crucial role in early hematopoiesis is well established, their function in endothelial cells and especially in angiogenesis is less understood. Here, we identified ANGIOPOIETIN-2 (ANG-2), which encodes a major regulator of angiogenesis, as a direct transcriptional target of TAL1, LYL1 and LMO2. Knockdown of any of the three transcription factors in human blood and lymphatic endothelial cells caused ANG-2 mRNA and protein down-regulation. Transient transfections showed that the full activity of the ANG-2 promoter required the integrity of a highly conserved Ebox-GATA composite element. Accordingly, chromatin immunoprecipitation assays demonstrated that TAL1, LYL1, LMO2 and GATA2 occupied this region of ANG-2 promoter in human endothelial cells. Furthermore, we showed that LMO2 played a central role in assembling TAL1-E47, LYL1-LYL1 or/and LYL1-TAL1 dimers with GATA2. The resulting complexes were able to activate endogenous ANG-2 expression in endothelial cells as well as in non-endothelial cells. Finally, we showed that ANG-2 gene activation during angiogenesis concurred with the up-regulation of TAL1 and LMO2. Altogether, we identified ANG-2 as a bona fide target gene of LMO2-complexes with TAL1 and/or LYL1, highlighting a new function of the three hematopoietic factors in the endothelial lineage.
Institut de Génétique Moléculaire de Montpellier UMR 5535 CNRS, Montpellier, France.
Virginie
V
Deleuze
Rawan
R
El-Hajj
Elias
E
Chalhoub
Christiane
C
Dohet
Valérie
V
Pinet
Philippe
P
Couttet
Danièle
D
Mathieu
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D042702:Angiopoietin-2 / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017124:Conserved Sequence; D050989:GATA2 Transcription Factor / Q000502:physiology; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D060588:LIM Domain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D049409:Luciferases, Firefly / Q000096:biosynthesis / Q000235:genetics; D055806:Microvessels / Q000166:cytology; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D055503:Protein Multimerization; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014158:Transcription, Genetic
D048868:Adaptor Proteins, Signal Transducing; D042702:Angiopoietin-2; D051792:Basic Helix-Loop-Helix Proteins; D050989:GATA2 Transcription Factor; D060588:LIM Domain Proteins; D049409:Luciferases, Firefly; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; C494711:GATA2 protein, human; C085117:LMO2 protein, human; C086541:LYL1 protein, human; C067143:TAL1 protein, human