Nuclear and mitochondrial DNA-dependent RNA polymerases in bovine spermatozoa

Abstract

DNA-dependent RNA polymerases have been solubilized from separated head and tail fractions from normal bovine spermatozoa and from spermatozoa carrying the 'decapitated sperm defect'. When enzyme extracts from separated heads and tails were chromatographed on DEAE-Sephadex, the head fraction was resolved into 2 distinguishable peaks eluting at about 0.11 and 0.15 M-(NH4)2SO4 while the tail fraction yielded 4 distinct peaks eluting at about 0.11, 0.15, 0.255 and 0.35 M-(NH4)2SO4. Results indentical to those observed for sperm tails were obtained with extracts prepared from highly purified mitochondria from bovine or murine heart or liver. Optimization of reaction parameters and inhibitor studies with alpha-amanitin and rifampicin revealed strong similarities between eucaryotic nuclear RNA polymerases 1 and 2 and the 2 RNA polymerases associated with sperm heads. Similar experiments comparing the RNA polymerases from somatic mitochondria and sperm tails suggested the sperm tail enzymes were mitochondrial in origin.