Comparison of polysomal polyadenylated RNA from embryonal carcinoma and committed myogenic and erythropoietic cell lines

Abstract

Using the technique of mRNA-cDNA hybridization, we have examined the polysomal poly(A) + mRNA base-sequence complexity in three different mouse cell lines: mouse embryonal carcinoma cells, myoblast cells and Friend erythroleukemic cells. These cells express 7700, 13,200 and 6200 mRNA sequences, respectively, distributed in three frequency classes. Reciprocal heterologous hybridization experiments revealed that there is a large degree of homology, a subset of 6000 common sequences being present on the polysomes of all three cell types. Myoblast mRNA is capable of hybridizing all reactive embryonal carcinoma cell cDNA, with kinetics close to the homologous embryonal carcinoma cell curve, thus indicating that all embryonal carcinoma cell sequences are present on myoblast polysomes, the majority at similar abundance. Conversely, embryonal carcinoma cell mRNA fails to hybridize 12% of myoblast cDNA, apparently arising primarily from the complex frequency class. This was confirmed by using myoblast fractions partially enriched in abundant and rare sequences. As a proportion of the rare class, this 12% fraction represents about 4500 sequences close to the difference in base-sequence complexity between myoblast and embryonal carcinoma cells. Homologous and heterologous hybridization with total and fractionated Friend cell cDNA probes revealed that all Friend cell polysomal poly(A) + RNA sequences are common to embryonal carcinoma cell polysomes—apart from a small group of sequences drawn from the abundant class, corresponding to about 10% of Friend cell cDNA. This represents about 12 sequences from the abundant class. In addition, certain common sequences in the abundant Friend cell frequency class are present at lower frequency in embryonal carcinoma cell polysomes. Friend cell polysomal poly(A) + RNA fails to hybridize 7–10% embryonal carcinoma cell cDNA apparently derived from the rare frequency class. As a fraction of the rare class, this corresponds approximately to the difference (about 1500 sequences) in complexity between the Friend and embryonal carcinoma cell lines.