A novel member of the glycosyltransferase family, beta 3 Gn-T2, highly downregulated in invasive human bladder transitional cell carcinomas.

Abstract

Differential display reverse transcription (DDRT)-polymerase chain reaction (PCR) was used to compare the transcriptomes of invasive and noninvasive fresh human bladder transitional cell carcinomas. A differentially expressed novel gene sharing structural similarity with the human beta 3-galactosyltransferase family, beta-1,3-N-acetylglucosaminyltransferase-T2 (beta 3Gn-T2), was identified. The full-length beta 3Gn-T2 cDNA, containing a complete open reading frame of 1193 bp, was cloned and sequenced. beta 3Gn-T2 exhibited 29-41% homology to the multigene beta 3-galactosyltransferase family. Expression of the full-length beta 3Gn-T2 cDNA in an in vitro coupled transcription/translation assay yielded a primary translation product with an apparent Mr of 46 kDa, which is in agreement with the predicted 397-amino-acid protein encoded by beta 3Gn-T2. Multiple peptide alignment showed several sequence motifs corresponding to putative catalytic domains that are conserved throughout all members of the beta 3-galactosyltransferase family, namely, a type II transmembrane domain, a conserved DxD motif, an N-glycosylation site, and five conserved cysteins. By RT-PCR strong downregulation of beta 3Gn-T2 expression was noted in invasive human bladder transitional cell carcinomas (16 fresh biopsy samples: grade III, T2-T4) compared with their noninvasive counterparts (15 fresh biopsies: grade II, Ta), suggesting that beta 3Gn-T2 may be involved in cancer progression.