[mRNA fractions of mouse plasmacytoma cells].

The sedimentation characteristics of polysomal mRNA labelled in vitro by [5-3H]uridine and electrophoretic mobility of similar non-labelled mRNA of mouse plasmacytoma were studied. Rapidly labelled polysomal mRNA may be considered as mRNA on the basis of several independent but indirect tests. These mRNA's are localized in 18-6S region of sucrose gradient. Some part of radioactivity have been found in the ribosomal RNA. It was shown that there is 8-10 RNA fractions in sucrose gradient. The 16S and 12-14S fractions are isolated and partially purified by two- and three-fold centrifugation. Fractions homogenous in sucrose gradient were electrophoresed in PAAG-SDS and divided into several subfractions some of them being common for 16S and 12-14S. The number of non-crossover subfractions was about 2-3. Not less than 20 different main fractions of polysomal mRNA were determined in plasmacytoma cells on the basis of electrophoretic data.