Arrest-defective-1 Protein, an Acetyltransferase, Does Not Alter Stability of Hypoxia-inducible Factor (HIF)-1α and Is Not Induced by Hypoxia or HIF

The hypoxia-inducible factor (HIF) is a key player in a transcriptional pathway that controls the hypoxic response of mammalian cells. Post-translational modification of the α subunit of HIF determines its half-life and activity. Among the multiple reported modifications, acetylation, by an acetyltransferase termed arrest-defective-1 protein (ARD1), has been reported to decrease HIF-1α stability and therefore impact on hypoxic gene expression. In contrast, we report that both overexpression and silencing of ARD1 had no impact on the stability of HIF-1α or -2α and that cells silenced for ARD1 maintained hypoxic nuclear localization of HIF-1α. In addition, we show that the ARD1 mRNA and protein levels are not regulated by hypoxia in several human tumor cell lines, including cervical adenocarcinoma HeLa cells, fibrosarcoma HT1080 cells, adenovirus-transformed human kidney HEK293 cells, and human breast cancer MCF-7 cells. Using two model systems ((a) wild-type and HIF-1α-null mouse embryo fibroblasts and (b) HeLa cells silenced for HIF-1α or -2α by RNA interference), we demonstrate that the level of expression of the ARD1 protein is independent of HIF-1α and -2α. We also demonstrate that ARD1 is a stable, predominantly cytoplasmic protein expressed in a broad range of tissues, tumor cell lines, and endothelial cells. Taken together, our findings demonstrate that ARD1 has limited, if any, impact on the HIF signaling pathway. The hypoxia-inducible factor (HIF) is a key player in a transcriptional pathway that controls the hypoxic response of mammalian cells. Post-translational modification of the α subunit of HIF determines its half-life and activity. Among the multiple reported modifications, acetylation, by an acetyltransferase termed arrest-defective-1 protein (ARD1), has been reported to decrease HIF-1α stability and therefore impact on hypoxic gene expression. In contrast, we report that both overexpression and silencing of ARD1 had no impact on the stability of HIF-1α or -2α and that cells silenced for ARD1 maintained hypoxic nuclear localization of HIF-1α. In addition, we show that the ARD1 mRNA and protein levels are not regulated by hypoxia in several human tumor cell lines, including cervical adenocarcinoma HeLa cells, fibrosarcoma HT1080 cells, adenovirus-transformed human kidney HEK293 cells, and human breast cancer MCF-7 cells. Using two model systems ((a) wild-type and HIF-1α-null mouse embryo fibroblasts and (b) HeLa cells silenced for HIF-1α or -2α by RNA interference), we demonstrate that the level of expression of the ARD1 protein is independent of HIF-1α and -2α. We also demonstrate that ARD1 is a stable, predominantly cytoplasmic protein expressed in a broad range of tissues, tumor cell lines, and endothelial cells. Taken together, our findings demonstrate that ARD1 has limited, if any, impact on the HIF signaling pathway. A strong relationship between hypoxia, angiogenesis, and tumor progression is emerging (1Hockel M. Vaupel P. J. Natl. Cancer Inst. 2001; 93: 266-276Crossref PubMed Scopus (2259) Google Scholar). The transcription factor, hypoxia-inducible factor (HIF), 1The abbreviations used are: HIF, hypoxia-inducible factor; ARD1, arrest-defective-1 protein; ERK, extracellular signal-regulated kinase; PHD, prolyl hydroxylase domain protein; SIMA, similar; siRNA, small interfering RNA; DMEM, Dulbecco's modified Eagle's medium; FCS, fetal calf serum; RT, reverse transcription. is the key player in the hypoxic response of cells by regulating the expression of a myriad of genes including those that control angiogenesis and neovascularization, such as the vascular endothelial growth factor (2Manalo D.J. Rowan A. Lavoie T. Natarajan L. Kelly B.D. Ye S.Q. Garcia J.G. Semenza G.L. Blood. 2005; 105: 659-669Crossref PubMed Scopus (935) Google Scholar, 3Schofield C.J. Ratcliffe P.J. Nat. Rev. Mol. Cell. Biol. 2004; 5: 343-354Crossref PubMed Scopus (1678) Google Scholar). The stability and, thus, activity of HIF-1α is regulated by multiple post-translational modifications, in particular hydroxylation and phosphorylation (4Brahimi-Horn C. Mazure N. Pouyssegur J. Cell Signal. 2005; 17: 1-9Crossref PubMed Scopus (191) Google Scholar). Hydroxylation by prolyl hydroxylase domain proteins (PHD) has been shown to mediate degradation by the ubiquitin-proteosomal system, and our group showed previously that the PHD2 isoform is a key oxygen sensor in determining HIF-1α stability (5Berra E. Benizri E. Ginouves A. Volmat V. Roux D. Pouyssegur J. EMBO J. 2003; 22: 4082-4090Crossref PubMed Scopus (1123) Google Scholar). The expression of this isoform was induced under hypoxia, thus suggesting the existence of feedback regulation. It has also been reported that the instability of HIF-1α is enhanced by its acetylation, by an acetyltransferase termed arrest-defective-1 protein (ARD1), and that ARD1 expression is repressed in hypoxia (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). We were interested in investigating further the contribution on the function of HIF that this post-translational modification had under different conditions but were surprised to find that ARD1, in contrast to PHD2, had no impact on HIF-1α stability and was not hypoxia- or HIF-α-dependent. ARD1 was first described in Saccharomyces cerevisiae (7Whiteway M. Szostak J.W. Cell. 1985; 43: 483-492Abstract Full Text PDF PubMed Scopus (119) Google Scholar), and yeast mutants for ARD1 were shown to be defective in the mitotic cell cycle. The human and mouse homologs have also been designated TE2 (Swiss-Prot; P41227 and Q9QY36, respectively). Based on amino acid alignment, ARD1 has been assigned to the GNAT (GCN5-related N-terminal acetyltransferase) family, of which there are over 50 members, and it possesses a conserved (Q/R)XXGX(G/A) acetyl-CoA binding motif (8Neuwald A.F. Landsman D. Trends Biochem. Sci. 1997; 22: 154-155Abstract Full Text PDF PubMed Scopus (390) Google Scholar), which is also conserved from yeasts to humans. ARD1 was found to interact with HIF-1α in a two-hybrid assay using a Gal4-HIF-1α-oxygen-dependent degradation domain vector as bait (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). The expressed HIF protein contains a domain, called the oxygen-dependent degradation domain, which is implicated in the regulation of the half-life of the three isoforms of HIF-α. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis showed in vitro acetylation of lysine 532 on a recombinant oxygen-dependent degradation domain fragment of HIF-1α in the of recombinant ARD1 (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). HIF-1α was in cell and of the lysine 532 to in stability of HIF-1α as also previously T. L. EMBO J. PubMed Google Scholar). of the of HIF-1α with a of in degradation of HIF-1α and with an with levels of HIF-1α protein Lee Lee E.J. Kim Lee Kim Kim K.W. Nat. 2001; PubMed Scopus Google Scholar). In addition, it has been that the of an of an from an in the acetylation of HIF-1α Lee Mol. 2004; Google Scholar). of HIF-1α was reported to HIF-1α protein by its with a (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). the the activity of is not to be on the oxygen It therefore be that ARD1 HIF-1α in both and HIF-1α was in hypoxia in with that HIF-1α was by of HT1080 cells in the of the in (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). The for this was that hypoxia ARD1 mRNA and a and hypoxic levels of ARD1 mRNA in cells L. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). The also report that the of genes such as vascular endothelial growth factor and is not by ARD1, suggesting that ARD1 has on In the we show that ARD1 overexpression or silencing has no impact on HIF-1α and -2α protein We on to the hypoxic regulation of the expression of ARD1 by that the mRNA the protein levels of ARD1 are regulated by or hypoxia in several cell We also show for the first that ARD1 expression is independent of HIF-1α and -2α. In addition, we show that ARD1 is predominantly cytoplasmic and that its silencing not nuclear of HIF-1α. We also show that the ARD1 protein is expressed in a broad range of tissues, tumor cell lines, and endothelial cells of different and that it has a Cell and and HT1080 cells were in Dulbecco's modified Eagle's with fetal calf and and MCF-7 cells were in embryo fibroblasts and were in with and amino cells were from wild-type and HIF-1α-null mouse as described previously M. D. M. Cancer Google Scholar). cell cells were in DMEM, endothelial cells were in with FCS, endothelial cells were in with FCS, and human endothelial cells were as previously described V. C. E. E. J. Cell Sci. 2002; PubMed Google Scholar). cells were in and were under or hypoxic conditions for the was in an the of the half-life of ARD1, cells were with or for and The of on ARD1 expression was for the A to ARD1 was of a to the amino of the human ARD1 to a of to a protein of and to were also in the A. Pouyssegur J. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, C. E. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, E. E. Roux D. Pouyssegur J. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). mouse mouse mouse and The mammalian expression by contains the of human ARD1 with a on its N-terminal and is to as The of human ARD1 was from using the with the and The a for and the of the of The the ARD1 by the of an which was used for The was the and of A that contains the were using a of or were using the and cell and of was as described mRNA levels of ARD1, and were by were in or hypoxia for the and the was by of were in and RNA was using the P. N. Biochem. PubMed Scopus Google Scholar). transcription of of RNA was using the independent of were used to and reverse The ARD1 have been previously Lee E. Bae E.J. Kim J.W. Cancer 2003; Google Scholar). The for HIF-1α were as for were as for used as a were and reverse on was using the for the ARD1 in a for for for for for and for of an of was also in a for the that were The ARD1 were on using the mRNA were with and with an were using the and from RNA as and mRNA silencing using was as previously described (5Berra E. Benizri E. Ginouves A. Volmat V. Roux D. Pouyssegur J. EMBO J. 2003; 22: 4082-4090Crossref PubMed Scopus (1123) Google Scholar, J.W. Ratcliffe P.J. Cancer 2003; Google Scholar). were as the The ARD1 used was as were for on two a of using the were in the and cell for were in and and in of using a assay was on were to and with were in in and in the of the and in in in and in the was with an from The are of two independent in were as for and were to on and in for with for with for and with the ARD1 or HIF-1α in for cells were in the of a to and the nuclear for were in of the was with a and were using was using a The laser and the were on and The and was The was maintained We used a The control was with a of and the was with a of were for using Cell HeLa cells were with a on for and for The nuclear was in and for protein using a was to the and and of protein for was by and using or of the to ARD1 for in and the expression and localization of the ARD1 we a a of the amino of the human ARD1 is conserved in the and in but not in D. or A was by of of HeLa cells to the of human ARD1, a protein of amino a mass of further the HeLa cells were with a ARD1 expression the ARD1 was The be to a modification in the and of the protein to the of the which was also with an not The to ARD1 was further by of the with ARD1 mRNA with a control to is also and was used as a The to ARD1 was for in HeLa cells by of cells with an ARD1 with the level of the from cells with a control showed an in the in the of ARD1 of and of the ARD1 the of the ARD1 for and and of ARD1 on HIF-1α and -2α and of ARD1 HIF-1α the of ARD1 on HIF-1α and -2α we ARD1 and cells under and and hypoxic HeLa cells were with a control or with a vector A and in the protein level for HIF-1α and -2α and was in or hypoxia between control cells and cells ARD1 with the The level of expression of both the and ARD1 of cells to or hypoxia for and the of the was with were of hypoxic not was also no in the stability of HIF-1α HT1080 cells were for in hypoxia not We that the of a in the of ARD1 has on HIF-1α stability in or In addition, silencing of ARD1 not have a impact on HIF-1α or -2α protein stability in or hypoxia, as for the and control to the control is in contrast to silencing of PHD2, as shown both and previously by our in of HIF-1α protein in (5Berra E. Benizri E. Ginouves A. Volmat V. Roux D. Pouyssegur J. EMBO J. 2003; 22: 4082-4090Crossref PubMed Scopus (1123) Google Scholar). to HIF-1α using several and Cell and were In addition, we were to in vitro acetylation of and lysine 532 with recombinant ARD1 not of HIF-1α by in with silencing of ARD1, and silencing not the nuclear localization of HIF-1α under hypoxic conditions of ARD1 not or hypoxic HIF-1α stability or its of HeLa cells in or hypoxia no or with a control an to ARD1, or an to PHD2 were by with and The on the was used as a HeLa cells with to and or to ARD1 and were in and or hypoxia and for and by for HIF-1α using a to was and the ARD1 mRNA and by and or by that the level of the mRNA of ARD1 were reported to be in HT1080 cells a or hypoxic (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar), we were interested to if this was a in tumor cells and if it was maintained under of this we regulation of the ARD1 mRNA and protein in several cell to and The mRNA levels were by in breast cancer MCF-7 and fibrosarcoma HT1080 cells to and of hypoxia We not in the mRNA expression levels cells in to cells in or hypoxia for MCF-7 cells and HT1080 cells of was used as a hypoxic regulation in cells the mRNA we the for the hypoxic of two hypoxia response and the of the genes were in The of hypoxic regulation of ARD1 was further by D. E. M. C. and J. in the that the previously reported decrease in expression in hypoxia was on the cell we cells different and ARD1 expression in no in the mRNA level was not A of for of the for ARD1, which was reported to show mRNA expression in HEK293 cells in hypoxia for Lee E. Bae E.J. Kim J.W. Cancer 2003; Google Scholar), was also on the RNA in no in expression levels was not on which were ARD1 mRNA not to be by or hypoxia or by We the protein levels of ARD1 were regulated by hypoxia, using in to those used for the described in of HT1080 cells to and of hypoxia not the expression levels of the ARD1 protein The of this was that were to cell The of the hypoxic was by the of HIF-1α under were for MCF-7 cells to hypoxic conditions not and no in the expression level of the ARD1 protein was for HeLa cells as shown in In addition, of cells under hypoxic conditions with or of for not to in the expression level of the ARD1 mRNA with not of hypoxia have no on ARD1 mRNA expression. further regulation of ARD1, two hypoxic to HIF-1α stability were The hypoxic HIF-1α and -2α by the and the subunit degradation C.J. Biol. PubMed Scopus Google Scholar). to not the ARD1 protein level in HeLa or cells of MCF-7 cells with hypoxia also not the protein expression levels not cells are in is and under conditions by and 2003; PubMed Scopus Google Scholar). also that the or of not the level of ARD1 We the between our findings in several cell and those for the HT1080 cells, has also been reported to in of HIF-1α M.A. D. 2001; PubMed Scopus Google we not a in the ARD1 protein by or in with hypoxia for the cell not ARD1 or the that HIF-1α have on ARD1 protein we wild-type and HIF-1α-null mouse embryo The of HIF-1α in hypoxic of and control HeLa cells and its in cells the of cells with to HIF-1α It is of that has been reported to be in mouse embryo fibroblasts C.J. Mol. Cell. Biol. 2003; PubMed Scopus Google Scholar, L. Mol. Cell. Biol. 2003; PubMed Scopus Google Scholar). levels of ARD1 protein were in both and cells. the of of in ARD1 mRNA and protein we silenced HIF-1α and in HeLa cells using and the level of ARD1 mRNA and protein has been for in our (5Berra E. Benizri E. Ginouves A. Volmat V. Roux D. Pouyssegur J. EMBO J. 2003; 22: 4082-4090Crossref PubMed Scopus (1123) Google and in a for J.W. Ratcliffe P.J. Cancer 2003; Google Scholar). with in a decrease in the HIF-1α mRNA and a decrease in mRNA with the for the with the control A analysis with the RNA showed no in the level of expression of ARD1 HIF-1α or -2α levels were The level of silencing for both proteins not the level of expression of the ARD1 protein In addition, HeLa cells silenced for HIF-1α or the ARD1 cytoplasmic localization as with those cells silenced with control siRNA, that the expression and the localization of ARD1 are independent of HIF-1α and -2α. ARD1 a of the ARD1 protein on the protein of protein and localization in amino acid a nuclear localization suggesting cytoplasmic as for cells with the control the for ARD1, is predominantly to the in cells to hypoxia, we the to ARD1 of cells in and conditions not the with or the localization of the ARD1 the the of cells analysis using were by analysis that ARD1 is predominantly to the a small of was the A predominantly cytoplasmic localization was was with that of the of in cells, the was with the thus, the in cells was further the cytoplasmic localization of ARD1, we and ARD1 was in the cytoplasmic The nuclear protein and the cytoplasmic were used to the of the nuclear and cytoplasmic ARD1 a of the stability of the ARD1 protein showed it to be stable, with a half-life of which is with that for The stability of the protein a protein in the of vascular endothelial growth factor with a half-life of was in C. E. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The stability was for ARD1 cells were in hypoxia not HIF-1α is to a in tumor progression and angiogenesis, we the expression of ARD1 in tumor and endothelial cells. We found that the ARD1 protein is expressed in a broad range of human tumor cell and in and endothelial cells to the expressed is shown for with the ARD1 of of showed that ARD1 protein was expressed in of the with the of the the to is shown by of in is to the to the of the of ARD1 function in endothelial cell and in tumor is expressed in several tumor cell and endothelial cells of different and is expressed in mouse analysis of of different tumor cell and endothelial cells, including human adenocarcinoma and cells, human cervical adenocarcinoma HeLa cells, human fibrosarcoma HT1080 cells, human breast cancer MCF-7 cells, endothelial cells adenovirus-transformed human kidney HEK293 cells, human endothelial cells endothelial cells and cells by and cells using the of ARD1 in of mouse of protein with the to the expressed protein was on the In contrast to a report by (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar), we demonstrate that overexpression silencing of ARD1 by RNA HIF-1α The report by (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google showed a decrease in the half-life of HIF-1α in cells and a of HIF-1α to hypoxic levels in HEK293 cells with an ARD1 we not a decrease in the level of HIF-1α or -2α ARD1 was In addition, we demonstrate that silencing of ARD1 not the level of HIF-1α or -2α in or hypoxia by silencing for PHD2 that in of HIF-1α in findings are by those of L. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar), showed that the mRNA levels of the and vascular endothelial growth factor, were in and HEK293 cells silenced for ARD1 by RNA of the proteins that HIF-1α are regulated by hypoxia, or which the existence of feedback two of the three human isoforms that HIF-1α are (5Berra E. Benizri E. Ginouves A. Volmat V. Roux D. Pouyssegur J. EMBO J. 2003; 22: 4082-4090Crossref PubMed Scopus (1123) Google Scholar, J. M. E. A. N. P. J. C.J. Ratcliffe P.J. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, E. P. M. C. T. J. J. Cell Sci. 2003; PubMed Scopus Google Scholar). have that ARD1 mRNA is regulated by hypoxia, two show no hypoxic regulation. The first that hypoxic by (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar), showed of the mRNA in HT1080 cells in hypoxia and or in the of the hypoxia a was with A decrease in the level of the protein was also reported by but The by Lee E. Bae E.J. Kim J.W. Cancer 2003; Google Scholar), showed of ARD1 mRNA and protein in HEK293 cells in hypoxia for In contrast, a report showed no hypoxic not regulation of ARD1 the mRNA level in cells and no or a on the mRNA level in and cells with L. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). not of were hypoxia which has been shown to the but also prolyl hydroxylase M. T. V. J.W. Natl. Sci. A. 2002; PubMed Scopus Google Scholar), in a decrease in ARD1 mRNA in and HEK293 cells. not the mRNA but also and ARD1 protein expressed in and HEK293 cells in or hypoxia or in the of the hypoxia and from several that ARD1 mRNA and protein are not regulated in cells by or hypoxia or by hypoxia in the cells. In addition, we and the oxygen level as to with reported are also by a by (2Manalo D.J. Rowan A. Lavoie T. Natarajan L. Kelly B.D. Ye S.Q. Garcia J.G. Semenza G.L. Blood. 2005; 105: 659-669Crossref PubMed Scopus (935) Google Scholar), which a of gene including those for ARD1, in human endothelial cells in or hypoxia and HIF-1α. not ARD1 as repressed or We further that ARD1 expression is not on HIF-1α or -2α by that the ARD1 levels are the in wild-type and cells or in cells in which HIF-1α or -2α were silenced by RNA is the of ARD1 in angiogenesis and on its in impact in cell ARD1 was to be in cell control in yeast (7Whiteway M. Szostak J.W. Cell. 1985; 43: 483-492Abstract Full Text PDF PubMed Scopus (119) Google Scholar), to be in in N. J. Biol. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar), and to be implicated in human cell L. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). a N-terminal ARD1 interact with N-terminal N. J. Biol. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, T. D. C. M. Biochem. J. 2005; PubMed Scopus Google Scholar, M. M. M. EMBO J. PubMed Scopus Google Scholar, Szostak J.W. EMBO J. PubMed Scopus Google Scholar). a cancer it is of to that the mouse N-terminal is implicated in vascular M. T. N. Biol. 2002; PubMed Scopus Google Scholar, Sci. 2001; Google Scholar, PubMed Scopus Google and therefore an in The human also termed or has been shown to be implicated in transcription of the gene N. J. Biol. 2002; Full Text Full Text PDF PubMed Scopus Google and is in 2002; PubMed Scopus Google and cancer A. A. E. J. 2002; PubMed Scopus Google Scholar). The if any, that ARD1 in as a we were interested in the expression of ARD1 in mouse tissues, tumor cell lines, and, in endothelial cells, which are to We that ARD1 is expressed levels in a broad range of tissues, tumor cell lines, and endothelial cells of different We also demonstrate that ARD1 is a protein by both and was predominantly to the a small of ARD1 was in the in nuclear with the we the that it in and of the by it is of small and not to a nuclear localization We also show that the ARD1 cytoplasmic localization in hypoxia and HIF-1α or -2α are silenced by RNA or ARD1 is expressed mouse and human ARD1 has also been shown by cell of HT1080 cells (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google and by of kidney fibroblasts N. J. Biol. 2003; Full Text Full Text PDF PubMed Scopus Google to be to the and human ARD1 were reported to be cytoplasmic and nuclear in HeLa cells by T. D. C. M. Biochem. J. 2005; PubMed Scopus Google Scholar). the silencing of the cytoplasmic and the of on for cells with ARD1 mRNA in this we are in that the of ARD1 is cytoplasmic in HeLa cells. that ARD1 in the on the levels of HIF-1α under conditions or on HIF-1α its to the acetylation of HIF-1α was reported by (6Jeong J.W. Bae M.K. Ahn M.Y. Kim S.H. Sohn T.K. Bae M.H. Yoo M.A. Song E.J. Lee K.J. Kim K.W. Cell. 2002; 111: 709-720Abstract Full Text Full Text PDF PubMed Scopus (617) Google Scholar). In our for the first that ARD1 silencing by RNA and overexpression of ARD1 not HIF-1α or -2α (b) that ARD1 silencing not HIF-1α the with to hypoxic regulation of ARD1 and its cytoplasmic that ARD1 is not an HIF-1α or and expression of that the of ARD1 in angiogenesis not HIF-1α regulation. levels of ARD1 are in tumor cell and endothelial cells, it is that ARD1 a to be in angiogenesis and tumor We of and of for the and mouse embryo fibroblasts and The for the cells. We and for and for with We for the ARD1 expression

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