Intracellular distribution of low molecular weight RNA species in HeLa cells.

Abstract

Intracellular distributions of the low MW RNA species of HeLa cells were determined by a nonaqueous method of cell fractionation, in which lyophilized cells were homogenized and centrifuged in anhydrous glycerol. The nonaqueous method was used to avoid artifactual extraction of weakly bound nuclear RNA during cell fractionation. The mature small RNA species K, A, C and D were almost entirely (> 95%) nuclear and mature 4S tRNA was partially (5-10%) nuclear. These results gave higher nuclear content of the mature species K, A, C and 4S than was shown previously with conventional aqueous cell fractionation. The nonaqueous method gave higher nuclear proportions of some short-lived precursors to mature small RNA. Approximately 1/2 of recently synthesized pre-4S RNA and more than 1/2 of recently synthesized 5S RNA were nuclear; these species were previously thought to be cytoplasmic. The species C'' and D'', precursors to the stable nuclear species C and D, respectively, were partially nuclear, in contrast to earlier work. The stable cytoplasmic species L (oncornavirus 7S RNA) was mostly nuclear shortly after synthesis.