ABSTRACT
【Objective】 To investigate the effects of the loss of exon 1 of TFE3 on nuclear localization of chimeric TFE3 protein in TFE3 translocation renal cell carcinoma (TFE3 tRCC). 【Methods】 The localization of TFE3 protein in TFE3 tRCC and clear cell renal cell carcinoma (ccRCC) were detected with immunochemistry. The exon retention of TFE3 gene in TFE3 tRCC was analyzed in databases and literatures. The plasmids containing TFE3 full-length and different-length of TFE3 exons which were constructed to pCDH-MCS-EGFP-Puro were transfected into HEK293T using Lipo FiterTM. The localization of EGFP protein in HEK293T cells were detected with confocal microscopy. The localization of TFE3 protein and truncated TFE3 protein were detected with Western blotting. The mRNA expression of the downstream genes of TFE3 protein were detected with q-PCR. 【Results】 Strong nuclear signal of TFE3 protein was observed in TFE3 tRCC, whereas TFE3 protein in ccRCC was mainly localized in cytoplasm. The results of fluorescence imaging and Western blotting showed that TFE3 full-length protein was expressed both in nucleus and cytoplasm, and the expression of truncated TFE3 protein was mainly localized in nucleus. The q-PCR analysis demonstrated that the deletion of exon 1 in TFE3 gene led to a higher transcriptional level of targeted genes of TFE3 protein. 【Conclusion】 The loss of exon 1 in TFE3 played a critical role in preventing TFE3 protein from entering the nucleus. In TFE3 tRCC, the loss of exon 1 in TFE3 gene leads to the nuclear localization of TFE3 fusion protein and activation of its downstream target genes. This mechanism promises to uncover the occurrence and development of TFE3 tRCC.