Abstract: Objective: To investigate the effects of SET protein on the regulation of spermiogenesis, we observe the proliferation and histone acetylation of spermatocyte cell line GC-2 spd. Methods: GC-2 spd cells were cultured in vitro and identified by the of spermatocytes’ marker LDHC(lactate dehydrogenase C) and TESK1(Testis-Specific Kinase 1). Immunoprecipitation Kit detect combination of SET and H4. The cells in control group were transfected with AdH1-siRNA/NS and experimental group were transfected with AdH1-siRNA/SET, then compare the proliferation between them. Immunoflourscence microscopy detect the and location of SET protein; Use Realtime RT-PCRand Western Blot to detect the of mRNA and protein. Results: GC-2 spd cells espress the spermatocyte marker LDHC and TESK1. SET protein is expressed in both cytoplasm and nucleus of GC-2 spg cells. Immunoprecipitation showed that SET can combine with H4. The of SET mRNA and protein transfected with AdH1-siRNA/SET was significantly decreased. Both of the cytoplasm and nucleusa SET decreased after infection by immunoflourscence microscopy; Proliferation was significantly inhibited and acetylation of H4 was increased after transfection (1.236±0.2549)( *P＜0.05); There was no significantly difference in mRNA of HATs and HDACs. Conclusions: SET protein was expressed in both cytoplasm and nucleus of GC-2 spd cells; Knockdown of SET protein inhibited proliferation; SET participated in the regulation of spermiogenesis by combining with H4 then regulated its acetylation level.

Key words: SET protein, spermiogenesis, spermatocyte, histone, histone acetylation