Purification of novel UBAP1 protein and its decreased expression on nasopharyngeal carcinoma tissue microarray

Recently, the UBAPl gene, a putative nasopharyngeal carcinoma (NPC) related gene, which is located at human chromosome 9p21-22 where loss of heterozygosity frequently occurs in NPC, was cloned. The present study aimed to explore the purification approach to UBAP1 protein and its expression pattern in NPC with tissue microarray. The full length coding sequence of UBAP1 was subcloned into a prokaryotic expression vector, pGEX-4T-2, and expressed in Escherichia coli as a GST-fusion protein. With modification of the purification method, GST-UBAP1 fusion protein achieved a high level of purity. The New Zealand rabbit was immunized with the purified fusion protein to prepare polyclonal antiserum following standard protocols. With this antiserum, high-throughput analysis of UBAP1 protein expression using immunohistochemistry was performed on self-made tissue microarrays consisting of 316 nasopharyngeal specimens from 148 NPC and 168 non-cancerous nasopharyngeal epithelia with different morphological features. Consequently, we found that there was a significant decrease in the percentage of positive expression in all NPC on protein levels for UBAP1 (23%), compared to that of the non-NPC (89%) (P<0.01). The result suggests that UBAP1 might be a potential effective diagnosis candidate for NPC and decreased expression of UBAP1 protein is a possible point of dysfunction along the pathogenesis pathway for NPC that may contribute to malignant transformation.