Ets-1-dependent expression of vascular endothelial growth factor receptors is activated by latency-associated nuclear antigen of Kaposi's sarcoma-associated herpesvirus through interaction with Daxx.
Vascular endothelial growth factor (VEGF) and its receptors are highly expressed in Kaposi's sarcoma (KS) lesion and play a key role in angiogenesis. Latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) has multiple functions related to viral latency and KSHV-induced oncogenesis. In this report, we have identified Daxx as a LANA-binding protein by co-immunoprecipitation analysis of HeLa cells stably expressing LANA. LANA associated with Daxx in a PEL cell line infected with KSHV. LANA and Daxx also bound in vitro, suggesting direct interaction. From the results of binding assays, a region containing the Glu/Asp-rich domain within LANA, and a central region including the second paired amphipathic helix within Daxx contributed to the interaction. To address the physiological significance of this interaction, we focused on a Daxx-mediated VEGF receptor gene regulation. We found that Daxx repressed Ets-1-dependent Flt-1/VEGF receptor-1 gene expression, and that LANA inhibited the repression by Daxx in a reporter assay. Analyses of flow cytometry and real-time PCR revealed that expression of VEGF receptor-1 and -2 in LANA-expressing human umbilical vein endothelial cells (HUVECs) significantly increased. Co-immunoprecipitation and immunoblotting experiments suggested that LANA-bound Daxx to inhibit the interaction between Daxx and Ets-1. Chromatin immunoprecipitation assays showed that Daxx associated with VEGF receptor-1 promoter in HUVECs, and that LANA expression reduced this association. These results suggested that LANA contributes to a high expression of VEGF receptors in KS lesion by interfering with the interaction between Daxx and Ets-1.
Murakami
Yuko
Y
Department of Bioactive Molecules, National Institute of Infectious Diseases, Tokyo 162, Japan.
Yamagoe
Satoshi
S
Noguchi
Kohji
K
Takebe
Yutaka
Y
Takahashi
Naoko
N
Uehara
Yoshimasa
Y
Fukazawa
Hidesuke
H
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000502:physiology*; D000956:Antigens, Viral / Q000737:chemistry / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D056970:Co-Repressor Proteins; D042783:Endothelial Cells / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000737:chemistry / Q000502:physiology*; D050784:Proto-Oncogene Protein c-ets-1 / Q000502:physiology*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D000956:Antigens, Viral; D002352:Carrier Proteins; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; C494041:ETS1 protein, human; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D050784:Proto-Oncogene Protein c-ets-1; C109540:latency-associated nuclear antigen; D040262:Receptors, Vascular Endothelial Growth Factor