The UBEIL gene isolated from the chromosome 3p21 region has an extremely reduced level of mRNA in lung cancer. Sequence analysis showed a 45% homology to the human ubiquitin-activating enzyme El at the amino acid level. To further characterize the protein product, we generated UBEIL protein-specific antibodies. Immunoblot analysis revealed a full-length gene product of approximately 112 kDa. Assessment of the level and distribution pattern of the UBEIL protein in normal and tumor tissue using the generated antibodies showed that the UBEIL protein was present in normal lung cells and non-lung cancer cell lines, but was undetectable in all 14 human lung cancer cell lines analyzed. This difference in expression of the UBEIL protein between normal lung tissue and lung tumor-derived cell lines suggests a possible involvement of an El-like protein in the origin and/or progression of lung tumors. (C) 2000 Wiley-Liss, Inc