Demonstration of free reverse transcriptase in the nuclei of embryonic tissues of the Japanese quail.

Reverse transcriptase is detected in the nuclei as well as the cytoplasm of normal uninfected Japanese quail embryonic tissues. At least 60% of the nuclear enzyme occurs in the free-form, whereas 85% of the cytoplasmic enzyme is bound to particles having a buoyant density equivalent to retroviral cores (1.19-1.22 g/ml). The enzyme is purified by ion-exchange chromatography and glycerol sedimentation gradients. It prefers oligo(dG) . poly(C) in Mg2+ to all other synthetic template-primers, and transcribes poly(A) containing RNAs. Information present in the above particles is endogenous indicating that RT is not derived from exogenous retrovirus.