Role of activating transcription factor 3 on TAp73 stability and apoptosis in paclitaxel-treated cervical cancer cells.
Taxol (paclitaxel) is a potent anticancer drug that has been found to be effective against several tumor types, including cervical cancer. However, the exact mechanism underlying the antitumor effects of paclitaxel is poorly understood. Here, paclitaxel induced the apoptosis of cervical cancer HeLa cells and correlated with the enhanced activation of caspase-3 and TAp73, which was strongly inhibited by TAp73beta small interfering RNA (siRNA). In wild-type activating transcription factor 3 (ATF3)-overexpressed cells, paclitaxel enhanced apoptosis through increased alpha and beta isoform expression of TAp73; however, these events were attenuated in cells containing inactive COOH-terminal-deleted ATF3 [ATF3(DeltaC)] or ATF3 siRNA. In contrast, paclitaxel-induced ATF3 expression did not change in TAp73beta-overexpressed or TAp73beta siRNA-cotransfected cells. Furthermore, paclitaxel-induced ATF3 translocated into the nucleus where TAp73beta is expressed, but not in ATF3(DeltaC) or TAp73beta siRNA-transfected cells. As confirmed by the GST pull-down assay, ATF3 bound to the DNA-binding domain of p73, resulting in the activation of p21 or Bax transcription, a downstream target of p73. Overexpression of ATF3 prolonged the half-life of TAp73beta by inhibiting its ubiquitination and thereby enhancing its transactivation and proapoptotic activities. Additionally, ATF3 induced by paclitaxel potentiated the stability of TAp73beta, not its transcriptional level. Chromatin immunoprecipitation analyses show that TAp73beta and ATF3 are recruited directly to the p21 and Bax promoter. Collectively, these results reveal that overexpression of ATF3 potentiates paclitaxel-induced apoptosis of HeLa cells, at least in part, by enhancing TAp73beta's stability and its transcriptional activity. The investigation shows that ATF3 may function as a tumor-inhibiting factor through direct regulatory effects on TAp73beta, suggesting a functional link between ATF3 and TAp73beta.
Oh
Yeo Kyoung
YK
Center for Biomedical Sciences, NIH, Seoul 122-701, Korea.
Lee
Hyun Jung
HJ
Jeong
Mi-Hee
MH
Rhee
Marie
M
Mo
Ji-Won
JW
Song
Eun Hyeon
EH
Lim
Joong-Yeon
JY
Choi
Kyung-Hee
KH
Jo
Inho
I
Park
Sang Ick
SI
Gao
Bin
B
Kwon
Yongil
Y
Kim
Won-Ho
WH
D051700:Activating Transcription Factor 3 / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D001665:Binding Sites; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013816:Thermodynamics; D015533:Transcriptional Activation / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000473:pathology*
D051700:Activating Transcription Factor 3; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D017239:Paclitaxel