We previously identified a 700-kb region of common allelic loss on 3p14.3→p14.2 in renal cell carcinoma (RCC). We further analyzed this region and constructed a sequence ready bacterial artificial chromosome (BAC) contig. This region was totally covered by six overlapping BAC clones and was roughly estimated to be 700 kb. Furthermore, we isolated a gene in this region that we termed TU3A. This gene encodes a protein consisting of 144 amino acids. Homology search did not show any significant similarities with known genes or proteins. Northern analysis with normal tissue identified a 3.0-kb transcript that was expressed ubiquitously. Although our mutation search using 37 primary RCCs as well as five RCC cell lines failed to detect any somatic alterations in the TU3A gene, two of five RCC cell lines had totally lost its expression. Considering the fact that we found no genetic alterations in TU3A, it is possible that some epigenetic alteration may have suppressed its expression. Copyright (C) 2000 S. Karger AG, Basel.