To clone and identify the gene encoding human ubiquitin binding enzym e 2 and study its expression pattern. Methods. According to the sequence of human EST

which is highly homologous to t he mouse ubiquitin binding/conjugating enzyme （E2）

primers were synthesized to screen the human fetal brain cDNA library. The gene was analyzed by bioinformati cs technique and its expression pattern was studied by using multiple tissue No rthern blot. Results. Two cDNA clones encoding human ubiquitin conjugating enzyme have been i solated and identified. Both containing the ubiquitin conjugating domain

the 2 cDNA clones are 88% identical in amino acid sequences and splicing isoforms to each other only with an exon excised to form the short sequence. They belong to a highly conserved and widely expressed E2 enzyme family. Northern blot shows th at they are expressed exclusively in adult human heart

placenta

and pancreas b ut no transcripts can be detected in brain

lung

liver

skeletal muscle or kidn ey. Conclusions. The gene encoding human ubiquitin binding enzyme is expressed under temporal control. As a key enzyme in the degradation of proteins

ubiquitin con jugating enzymes play a central role in the expression regulation on the level o f post translation.