Characterization of the association of two small molecular weight RNAs with eukaryotic polysomes

Previous studies of the adult rat cerebral cortex have shown that two of the small molecular weight RNAs, K and L, are primarily cytoplasmic in location and are present in significant quantities in the microsomal fraction. We have examined their appearance in microsomal preparations. The results demonstrate that both K and L are, in fact, associated with polyribosomes. In particular, it is shown that (i) K and L are present in both membrane-bound and free polysomes; (ii) removal of microsomal membranes with Triton X-100 does not alter their association with microsomal polysomes; (iii) all of the K and almost one-half of the L associated with rat liver polysomes are resistant to high salt washing; and (iv) K and L are present in rabbit reticulocyte-free polysome preparations. The protein synthesis inhibitors cycloheximide and aurintricarboxylic acid significantly alter the association of K and L with rabbit reticulocyte-free polysomes. It is concluded that K and L are transiently associated with polysomes during the process of protein synthesis.