Par-4 transcriptionally regulates Bcl-2 through a WT1-binding site on the bcl-2 promoter.
Elevated expression levels of the bcl-2 proto-oncogene have been extensively correlated with the appearance of androgen independence in prostate cancer. Although bcl-2 was first cloned as the t(14:18) translocation breakpoint from human follicular B cell lymphoma, the mechanism of overexpression of bcl-2 is largely undefined for advanced prostate cancer because there are no gross alterations in the gene structure. We investigated the role of the product of the prostate apoptosis response gene-4 (Par-4) and the product of the Wilms' tumor 1 gene (WT1) in the regulation of Bcl-2 expression in prostate cancer cell lines. We observed growth arrest and apoptosis, upon decreasing Bcl-2 protein and transcript in the high Bcl-2-expressing, androgen-independent prostate cancer cell line, by all-trans-retinoic acid treatment (ATRA), but this did not occur in the androgen-dependent cell line expressing low levels of Bcl-2. The decrease in the Bcl-2 protein and transcript following all-trans-retinoic acid treatment was accompanied by changes in localization of Par-4 and an induction in the expression of WT1 protein. In stable clones expressing ectopic Par-4 and in ATRA-treated cells, we observed decreased Bcl-2 protein and transcript. This was accompanied by an induction in WT1 expression. The involvement of WT1 in the Par-4-mediated down-modulation of Bcl-2 was further defined by blocking endogenous WT1 expression, which resulted in an increase in Bcl-2 expression. Finally, we detected Par-4 and WT1 proteins binding to a previously identified WT1-binding site on the bcl-2 promoter both in vitro and in vivo leading to a decrease in transcription from the bcl-2 promoter. We conclude that Par-4 regulates Bcl-2 through a WT1-binding site on the bcl-2 promoter. These data also identify Par-4 nuclear localization as a novel mechanism for ATRA-mediated bcl-2 regulation.
Cheema
Sangeeta K
SK
Department of Bioimmunotherapy, Section of Immunobiology and Drug Carrier, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Mishra
Sandip K
SK
Rangnekar
Vivek M
VM
Tari
Ana M
AM
Kumar
Rakesh
R
Lopez-Berestein
Gabriel
G
D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000502:physiology*; D017931:DNA Primers; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D016193:G1 Phase / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D025721:WT1 Proteins / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D025721:WT1 Proteins; C101296:prostate apoptosis response-4 protein; D014212:Tretinoin