From a human fetal-brain cDNA library we isolated a novel ubiquitin-conjugating enzyme. The cDNA, designated UBE2G, contained an open reading frame of 510 nucleotides encoding 170 amino acids. The predicted peptide product showed 74% identity at the amino acid level with UBC7 of C. elegans, a high degree of homology with UBC7s of other species, and significant homologies with other subgroups of UBCs. Northern-blot analysis revealed strong expression of 4.4-kb, 2.4-kb, and 1.6-kb transcripts in skeletal muscle. Weak expression was observed in 15 other tissues examined. Radiation-hybrid mapping localized this cDNA to chromosome band lq42.