Identification and characterization of cul‐3b, a novel hominine CUL‐3 transcript variant

Aim: To identify genes related to the human testis development by substrate hybridization technique. Methods: A human testis cDNA microarray was constructed and hybridized with probes prepared from human adult and fetal testes and spermatozoa mRNAs by reverse transcription reactions. The differentially expressed genes were sequenced. And a newly identified cullin‐3 (CUL‐3) transcript variant (designated cul‐3b) was bio‐informatically analyzed with an online Gen Bank database. Multi‐tissue reverse transcription polymerase chain reaction (RT‐PCR) was used to determine the tissue expression profile of cul‐3b. Results: Cul‐3b, a novel CUL‐3 transcript variant, was identified. The expression level of cul‐3b in adult testes was 3.79–fold higher than that in fetal ones. Cul‐3b differed from cul‐3 (including NM_003590 and AY337761) in the opening reading frame and had three internal ribosomal entry sites (IRESes) in the 5′‐UTR. These led to a 24 amino acid (aa) truncation at N‐terminus of CUL‐3b as compared with CUL‐3 and a more motivated expression pattern of cul‐3b under some strict circumstances. Additionally, cul‐3b expressed ubiquitously in human tissues according to multi‐tissue RT‐PCR. Conclusion: Cul‐3b is a novel transcript variant of CUL‐3, which may be important not only for the development of human testis but also for that of other organs.