A novel ubiquitin carboxyl terminal hydrolase is involved in toad oocyte maturation

Zhao Gui SUN^{1, 2, 3,*}, Wei Hua KONG^2,*, Yan Jun ZHANG², Shan YAN¹, Ji Ning LU¹, Zheng GU¹, Feng LIN¹, Jia Ke TSO^1,**

¹National Laboratory of Contraceptives and Devices Research, Shanghai Institute of Planned Parenthood Research, Shanghai 200032, China
²College of Life Science, Shandong University, Ji'nan 250100, China
³Shandong University of Traditional Chinese Medicine, Ji'nan 250014, China

p28, a 28kD protein from toad (Bufo bufo gargarizans) oocytes, was identified by using p13^suc1-agarose affinity chromatography. Sequence homology analysis of the full-length cDNA of p28(Gene Bank accession number: AF 314091) indicated that it encodes a protein containing 224 amino-acids with about 55% identities and more than 70% positives to human, rat or mouse UCH-L1, and contains homological functional domains of UCH family. Anti-p28 monoclonal antibody, on injecting into the oocytes, could inhibit the progesterone-induced resumption of meiotic division in a dose-dependent manner. The recombinant protein p28 showed similar SDS/PAGE behaviors to the native one, and promoted ubiquitin ethyl ester hydrolysis, a classical catalytic reaction for ubiquitin carboxyl terminal hydrolases (UCHs). The results in this paper reveal that a novel protein, p28, exists in the toad oocytes, is a UCH L1 homolog, was engaged in the process of progesterone-induced oocyte maturation possibly through an involvement in protein turnover and degradation.

Key words: p28, cDNA clone, recombinant expression, ubiquitin carboxyl terminal hydrolase, oocyte maturation.