Cloning, expression, and mapping of UBE2I, a novel gene encoding a human homologue of yeast ubiquitin-conjugating enzymes which are critical for regulating the cell cycle

From a human fetal-brain cDNA library we isolated a novel gene sharing significant homology with two yeast genes, UBC9 and hus5, which encode ubiquitin-conjugating enzyme 9 (UBC9). In yeast this protein is critical for normal mitosis, and seems to be closely involved in progression of G(2) to M phase of the cell cycle. The human-UBC9 (h-UBC9) cDNA, (gene symbol UBE21), contained an open reading frame of 474 nucleotides encoding 158 amino acids. Its predicted peptide showed respectively 56% and 66% identity (75% and 82% similarity) with the products of UBC9 and hus5. Northern-blot analysis revealed expression of three transcripts, 6.4 kb, 3.3 kb, and 1.35 kb, in all human tissues examined. This gene, UBE2I, was mapped to chromosome band 16p13.3 by FISH.