Small molecular weight monodisperse nuclear RNA

The nuceloplasm and nucleolus of HeLa cells contain six distinct low molecular weight species of RNA. Their size, as estimated from electrophoretic mobility, ranges from 100 to 180 nucleotides. These RNA species are long-lived and do not appear to be precursor to any cytoplasmic product. At least four of them are extensively methylated. Their base compositions range from 47 to 54% guanosine + cytidine. Similar species of nuclear RNA are found in mouse fibroblast cultures and in the developing chick embryo brain.