Role of cytosol in the stimulation of RNA transport in vitro during cardiac hypertrophy in rats.

The 100,000 g supernatant isolated from hypertrophic hearts on fractionation by (NH4)2SO4 and DEAE-cellulose chromatography showed an enhanced RNA-transport activity when incubated with isolated nuclei from sham-operated hearts in vitro. Proteins of Mr 73,000, 68,000, 43,000 and 32,000 are enriched in the DEAE-cellulose fractions exhibiting maximal transport activity, and they are phosphorylatable. Pretreatment of the cytosol with antibodies to the Mr-68,000 and -32,000 proteins decreases the transport activity of the cytosol from 14% to 4.25%. Proteins of Mr 73,000, 68,000, 43,000 and 32,000 are translocated from the cytosol to the nuclear envelope under conditions of RNA transport in vitro. Our results here suggest that at least two of these proteins, those of Mr 68,000 and 32,000, play an indispensible role in the nucleocytoplasmic RNA transport in vitro. By making use of a specific myosin heavy-chain B-gene probe and hybridization, we have also shown the effect of cytosol on the transport of myosin heavy-chain mRNA from nucleus to cytosol.