HGNC Approved Gene Symbol: UPK1B
Cytogenetic location: 3q13.32 Genomic coordinates (GRCh38): 3:119,173,598-119,205,143 (from NCBI)
The asymmetric unit membrane (AUM) of mammalian bladder epithelium is believed to be involved in strengthening and stabilizing the urothelial apical surface, thus preventing the cells from rupturing during bladder distention. The major protein components of the AUM are UPK1A (611557), UPK1B, UPK2 (611558), and UPK3 (UPK3A; 611559) (Yu et al., 1994).
Yu et al. (1994) cloned cDNAs encoding bovine Upk1a and Upk1b and found that they are homologous to proteins in the 4 transmembrane (4TM), or tetraspan, family. Members of this family, which include CD37 (151523), CD53 (151525), CD63 (155740), and CD151 (602243), are integral membrane proteins that contain 4 predicted transmembrane domains (TMDs). TMDs 3 and 4 of Upk1a and Upk1b are connected by a long hydrophilic loop that contains 6 highly conserved cysteine residues and a potential N-glycosylation site. Yu et al. (1994) stated that all UPKs have large exoplasmic domains but very small cytoplasmic ones.
Finch et al. (1997) cloned a partial-length cDNA encoding human UPK1B by PCR. This 693-bp cDNA shows 91% homology to bovine Upk1b.
Using RT-PCR, Lobban et al. (1998) found that UPK1B was expressed in all normal human urothelial cell lines examined. In situ hybridization showed UPK1B in both superficial and upper intermediate cells of normal human urothelium. No expression was detected in the non-urothelial tissues examined. In contrast to the expression of other uroplakins, UPK1B was expressed in neoplastic urothelium and highly expressed in moderately differentiated transitional cell carcinomas (TCCs).
Using primers based on bovine Upk3, Yuasa et al. (1998) cloned UPK1B from normal human bladder total RNA. The deduced protein contains 287 amino acids. RT-PCR detected UPK1B and UPK3 in both normal and cancerous urothelial tissues. Both genes were also detected in the peripheral blood of 3 patients with metastatic TCC, but not in that from 9 patients with nonmetastatic TCC or in 3 healthy volunteers.
Olsburgh et al. (2002) determined that the UPK1B gene contains 8 exons and spans 31 kb. Exon 1 is noncoding, and intron 1 spans 13 kb. The promoter regions contains a CAATT box and binding sites for AP1 (see JUN; 165160), AP4 (600743), and SP1 (189906), but it does not have a TATA box. A canonical poly(A) signal and a noncanonical poly(A) signal are about 17.5 and 18.4 kb downstream of the ATG, respectively.
By radioisotopic in situ hybridization, Finch et al. (1997) mapped the UPK1B gene to 3q13.3-q21. Webb et al. (1999) mapped the mouse Upk1b gene to chromosome 16.
Finch, J. L., Webb, G. C., Evdokiou, A, Cowled, P. A. Chromosomal localization of the human urothelial tetraspan gene, UPK1B, to 3q13.3-q21 and detection of a Taq1 polymorphism. Genomics 40: 501-503, 1997. [PubMed: 9073521] [Full Text: https://doi.org/10.1006/geno.1996.4589]
Lobban, E. D., Smith, B. A., Hall, G. D., Harnden, P., Roberts, P., Selby, P. J., Trejdosiewicz, L. K., Southgate, J. Uroplakin gene expression by normal and neoplastic human urothelium. Am. J. Path. 153: 1957-1967, 1998. [PubMed: 9846985] [Full Text: https://doi.org/10.1016/S0002-9440(10)65709-4]
Olsburgh, J., Weeks, R., Selby, P., Southgate, J. Human uroplakin 1b gene structure and promoter analysis. Biochim. Biophys. Acta 1576: 163-170, 2002. [PubMed: 12031497] [Full Text: https://doi.org/10.1016/s0167-4781(02)00304-4]
Webb, G. C., Finch, J. L., Cowled, P. A. Assignment of the uroplakin 1b (Upk1b) gene to mouse chromosome 16 bands B5-C2 by in situ hybridization. Cytogenet. Cell Genet. 84: 37-38, 1999. [PubMed: 10343097] [Full Text: https://doi.org/10.1159/000015208]
Yu, J., Lin, J.-H., Wu, X.-R., Sun, T.-T. Uroplakins Ia and Ib, two major differentiation products of bladder epithelium, belong to a family of four transmembrane domain (4TM) proteins. J. Cell Biol. 125: 171-182, 1994. [PubMed: 8138569] [Full Text: https://doi.org/10.1083/jcb.125.1.171]
Yuasa, T., Yoshiki, T., Tanaka, T., Kim, C. J., Isono, T., Okada, Y. Expression of uroplakin Ib and uroplakin III genes in tissues and peripheral blood of patients with transitional cell carcinoma. Jpn. J. Cancer Res. 89: 879-882, 1998. [PubMed: 9818021] [Full Text: https://doi.org/10.1111/j.1349-7006.1998.tb00643.x]