Cytoplasmic ribonucleoproteins contain an abbreviated form of RNA L

RNA L, a molecule of 295 nucleotides synthesized by RNA polymerase III, is unique in that elements of homology to its sequence are frequently found within messenger RNAs and their precursors. In the course of an investigation of the small-RNA-containing RNPs of Chinese hamster cells, we have found an RNA species, Ls, which is similar to RNA L but about 100 nucleotides smaller. Here we show that Ls lacks a continuous sequence of nucleotides from the 3' Alu-like end of L. L-RNP has been shown to undergo transient association with ribosomes and has recently been postulated to regulate the synthesis and cotranslational insertion of integral membrane proteins through the endoplasmic reticulum