Cloning and characterization of the novel chimeric gene p53/FXR2 in the acute megakaryoblastic leukemia cell line CMK11-5.
The loss of p53 function is a key event in tumorigenesis. Inactivation of p53 in primary tumors and cell lines is mediated by several molecular mechanisms, including deletions and rearrangements. However, generation of a p53 fusion gene has not yet been reported. Here we report a novel p53/an autosomal homolog of the fragile X mental retardation (FXR2) chimeric gene generated by an interstitial deletion. Western blot analyses have shown that the p53/FXR2 protein is indeed expressed in a Down syndrome-related acute megakaryoblastic leukemia cell line, CMK11-5 cells. To investigate the properties of the p53/FXR2 protein, we observed its subcellular localization. Flag-tagged expression vectors were transfected into COS-7 cells and the proteins were stained with an anti-Flag antibody. The p53/FXR2 protein was expressed at high levels in the cytoplasm, whereas wild-type p53 and FXR2 were localized primarily in the nucleus and in the periphery of the nucleus, respectively. Treatment with a topoisomerase II inhibitor, VP16, failed to induce expression of a p53 target gene, the cyclin-dependent kinase inhibitor p21(WAF-1/CIP1), in CMK11-5 cells, and transient transfection analysis showed that the p53/FXR2 protein failed to transactivate the p21(WAF-1/CIP1) promoter. These results suggest that the p53/FXR2 fusion protein lacks the ability of wild-type p53 to function as a transcription factor. The p53/FXR2 gene is the first reported p53 fusion gene.
Kanezaki
Rika
R
Department of Pediatrics, Hirosaki University School of Medicine, Japan.
Toki
Tsutomu
T
Xu
Gang
G
Narayanan
Ramswamy
R
Ito
Etsuro
E
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D020869:Gene Expression Profiling; D016158:Genes, p53 / Q000235:genetics*; D006801:Humans; D007947:Leukemia, Megakaryoblastic, Acute / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D050506:Mutant Chimeric Proteins / Q000235:genetics*; D041681:NIH 3T3 Cells; D016601:RNA-Binding Proteins / Q000235:genetics*; D059005:Topoisomerase II Inhibitors
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C096915:FXR2 protein, human; D050506:Mutant Chimeric Proteins; D016601:RNA-Binding Proteins; D059005:Topoisomerase II Inhibitors; D005047:Etoposide