Regulation of oncogenic transcription factor hTAFII68-TEC activity by human glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

Abstract

Tumour-specific chromosomal rearrangements are known to create chimaeric products with the ability to generate many human cancers. hTAFII68-TEC (where hTAFII68 is human TATA-binding protein-associated factor II 68 and TEC is translocated in extraskeletal chondrosarcoma) is such a fusion product, resulting from a t(9;17) chromosomal translocation found in extraskeletal myxoid chondrosarcomas, where the hTAFII68 NTD (N-terminal domain) is fused to TEC protein. To identify proteins that control hTAFII68-TEC function, we used affinity chromatography on immobilized hTAFII68 (NTD) and MALDI-TOF (matrix-assisted laser-desorption ionization–time-of-flight) MS and isolated a novel hTAFII68-TEC-interacting protein, GAPDH (glyceraldehyde-3-phosphate dehydrogenase). GAPDH is a glycolytic enzyme that is also involved in the early steps of apoptosis, nuclear tRNA export, DNA replication, DNA repair and transcription. hTAFII68-TEC and GAPDH were co-immunoprecipitated from cell extracts, and glutathione S-transferase pull-down assays revealed that the C-terminus of hTAFII68 (NTD) was required for interaction with GAPDH. In addition, three independent regions of GAPDH (amino acids 1–66, 67–160 and 160–248) were involved in binding to hTAFII68 (NTD). hTAFII68-TEC-dependent transcription was enhanced by GAPDH, but not by a GAPDH mutant defective in hTAFII68-TEC binding. Moreover, a fusion of GAPDH with the GAL4 DNA-binding domain increased the promoter activity of a reporter containing GAL4 DNA-binding sites, demonstrating the presence of a transactivation domain(s) in GAPDH. The results of the present study suggest that the transactivation potential of the hTAFII68-TEC oncogene product is positively modulated by GAPDH.