A gene that could be potentially involved in spermatogenesis was identified and characterized by using suppression subtractive hybridization (SSH) and rapid amplification of cDNA ends (RACE) with total RNA from type A spermatogonia and pachytene spermatocytes of rat. This gene consists of 3 433 base pairs (bp) with a complete open reading frame (ORF) of 3 171 bp and encodes a putative protein containing 1057 amino acids. The nucleotide sequence displays a 93% identity to mouse ubiquitin-activating enzyme E1, Chr Y 1 (Ube1y1) and an 82% identity to human ubiquitin-activating enzyme E1 (UBE1). The putative protein of this gene contains an ubiquitin-activating enzyme signature 1 and an ubiquitin-activating enzyme active site, which are also existed in mouse ubiquitin-activating enzyme E1, human ubiquitin-activating enzyme E1 et al. So we named this gene as Rattus norvegicus ubiquitin-activating enzyme E1 (Ube1). The sequence of Ube1 was submitted to GenBank and the accession number is EF690356. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that Ube1 was specifically expressed in testis, while its expression was not detected in heart, brain, spleen, lung, liver, muscle, kidney and ovary. Comparison of the expression of Ube1 in different developmental stages of testis and Sertoli cells (real-time PCR) indicated that Ube1 was expressed more highly in spermatogonia than in spermatocytes, spermatids and Sertoli cells. In conclusion, Ube1 is a gene encoding rat ubiquitin-activating enzyme E1 and specifically expressed in testis, which might play a key role in ubiquitin system and influence spermatogenesis.