Poly(ADPR) polymerase-1 and poly(ADPR) glycohydrolase level and distribution in differentiating rat germinal cells

Poly( ADP-ribose) polymerase (PARP-1) and poly( ADP-ribose) glycohydrolase (PARG) are responsible for the transient poly( ADP-ribosyl) ation of proteins in eukaryotic cells. This biochemical reaction plays an active role in DNA replication and repair, transcription, cell differentiation and death. The aim of this study was to investigate the levels and the sub-cellular distribution of such enzymes in rat germinal cells at different stages of differentiation, i.e. in primary spermatocytes and round spermatids, representing meiotic and post-meiotic cells, respectively. The determination of the level of PARP-1 mRNA and protein revealed its higher expression in primary spermatocytes, thus implying that PARP-1 is one of the meiotic genes whose expression is requested at the pachytene phase of the meiosis. We also demonstrated that rat germinal cells contain both the forms of PARG (i.e. of 110 and 60 kDa) so far described in somatic cells. In our experimental system, the large PARG was present and active mainly in the nuclear fraction of primary spermatocytes, whereas round spermatids showed a higher level of the 60 kDa PARG in the post-nuclear fraction. Collectively, our data show a different expression level of PARP-1 and a different endocellular distribution of PARG and suggest a role for the poly( ADP-ribose) turnover in distinct pathways in meiotic and post-meiotic germinal cells.