Effects of Oestradiol-17P on the Synthesis of Uterine Heterogeneous Nuclear Ribonucleic Acid

glutaraldehyde before density analysis in CsCl gradients, which gave a particle density of 1.38g/cm3, indicating the characteristic protein:RNA ratio (w/w) of 4:l of hnRNAprotein particles (Samarina et al., 1967). When isolated 3H-labelled particles were incubated at 37°C for 1 h, a shift to lower sedimentation values was observed. However, there was no detectable loss of 3H radioactivity from the endogenous hnRNA to an acid-soluble form. On the other hand, if labelled hnRNA-protein particles were prepared by using the above methods and incubated with exogenous 3H-labelled HeLa-cell hnRNA there was a notable conversion of this RNA into molecules of lower molecular weight (approx. 6S), as judged by sedimentation in formamide-containing sucrose gradients.