Hepatocarcinogen-induced alterations in nuclear RNA compartmentation.

Prelabeled rat liver nuclei were purified, detergent-rinsed to remove cytoplasmic RNA contaminants and incubated in two in vitro RNA transport assays. Appropriate compartmentation of nuclear RNA sequences was maintained in an assay containing polyvinylpyrrolidone (PVP), which prevents nuclear swelling in aqueous media. Under these conditions, poly(A)+ RNA released in the presence of PVP (and ATP) was significantly more active in directing in vitro protein synthesis than poly(A)+ RNA released in the absence of either additive. Further, the excised fifth intron of alpha 1-acid glycoprotein remained nucleus-restricted, while release of poly(A)+ processing catabolites occurred in the absence of PVP. The appropriate compartmentation of nuclear sequences was lost following treatment of rats with the hepatocarcinogen thioacetamide, paralleling the in vivo situation. This assay should prove useful for subsequent studies on nucleocytoplasmic RNA transport in vitro, in particular for investigations relating to the altered RNA transport associated with the initiation of carcinogenesis.