| Abstract: | RNA molecules which are restricted to the nucleus in mouse L-cells were characterized by the technique of RNA/DNA hybridization. Competition of cytoplasmic RNA with labeled nuclear RNA of various sizes revealed that the RNA restricted to the cell nucleus is heterogeneous in size. Competition for sites on fractions of mouse DNA of various base compositions indicated that this unstable RNA is also heterogeneous in base composition. Fractionation of nuclei into three subfractions failed to separate the uniquely nuclear RNA from the precursors of cytoplasmic RNA. The significance of the selective transport of RNA from the nucleus to the cytoplasm and its importance in the control of gene activity in eucaryotic cells is discussed. |
