1. J. L. Chen and F. J. Longo (1996) Expression and localization of DNA topoisomerase II during rat spermatogenesis. Mol Reprod Dev 45(1): 61-71.
Abstract The potential role(s) of DNA topoisomerase II (topo II) during chromatin changes that characterize different stages of spermatogenesis was investigated in the rat by an analysis of the expression and localization of topo II mRNA and protein in individual spermatogenic cells. Expression of topo II was restricted to spermatogonia, spermatocytes, and round and early-elongating spermatids. Two protein bands of 177 and 170 kDa were detected in immunoblots of spermatocytes and round spermatids, while bands of 148 and 142 kDa were prominent in preparations of elongating spermatids. Topo II levels and distribution patterns, as observed by immuno-fluorescent microscopy, exhibited cell type-specific variations. Differences in topo II staining patterns were also apparent when nuclear matrices of spermatogenic cells were prepared with different extraction conditions. In addition to its possible function as a structural component, topo II, associated with nuclear matrix preparations from spermatogenic cells, possessed catalytic activity. These observations indicate that both the 177 and 170 kDa and the 148 and 142 kDa forms of topo II share similar structural and functional properties. Topo II beta mRNA was transcribed in rat spermatogenic cells at 6.2 kb. Relative levels of topo II beta mRNA were high in spermatogonia and spermatocytes, and decreased in both round and early-elongating spermatids. Changes in topo II expression levels and localization patterns represent distinct stage-specific markers for the maturation of spermatogenic cells, and are consistent with the involvement of topo II in mediating DNA modifications and chromatin changes during spermatogenesis. PMID: [8873071]
2. R. P. Bakshi, S. Galande, P. Bali, R. Dighe and K. Muniyappa (2001) Developmental and hormonal regulation of type II DNA topoisomerase in rat testis. J Mol Endocrinol 26(3): 193-206.
Abstract Type II DNA topoisomerase (topo II) is required for diverse biological functions including DNA replication, maintenance of genome stability, chromosome segregation and chromosome condensation. While the identity of topo II in rodent testis has been established, the regulation of topo II expression during the development of the postnatal testis and gametogenesis is unclear. Here, we report that rat testis topo II is developmentally and hormonally regulated. Topo IIalpha mRNA levels peaked prior to the onset of puberty, declined sharply thereafter and stabilized in adult testis. In contrast, the topo II enzyme content was lower in prepubertal testis but increased after the onset of puberty. Topo II was expressed in a cell-specific manner within germ cells, being detected only in pachytene spermatocytes. While testosterone markedly increased topo IIalpha mRNA levels in prepubertal testis, continued treatment failed to enhance topo IIalpha mRNA above postpubertal control levels. The extent of topo II activity remained steady regardless of the testosterone-induced increase in topo IIalpha mRNA levels. Inhibition of testosterone function in postpubertal animals by ethanedimethane sulphonate (EDS) and flutamide resulted in a significant decrease in topo IIalpha gene expression and topo II activity. The administration of exogenous testosterone (T) to EDS- and flutamide-treated rats restored topo IIalpha mRNA levels and topo II activity similar to the levels seen in the testis of age-matched control animals. Histochemical analyses of testes indicated that the effect of T on spermatogenesis was separable from its effect on topo IIalpha expression. Our results reveal that testosterone acts as a positive regulator of topo IIalpha gene expression and is required for the maintenance of topo IIalpha expression during the development of the postnatal testis and spermatogenesis. PMID: [11357056]
Figures for illustrating the function of this protein/gene
Function
Control of topological states of DNA by transientbreakage and subsequent rejoining of DNA strands. Topoisomerase IImakes double-strand breaks (By similarity).