ON RNA IN CULTURED MYELOMA CELLS PRODUCING IMMUNOGLOBULIN

The results of an investigation of RNA in a cell strain secreting immunoglobulin (MOPC 21) growing in cell culture are reported. Most of the cytoplasmic RNA is found in the polysomes, about half of which are associated with a membrane fraction. In several cell types the amount of RNA associated with the membranes varies and is correlated with the cell's ability to produce and secrete the antibody-like protein. In MOPC 21 both classes of polysomes are only degraded slowly in the presence of 5 μg/ml of actinomycin D. In an analysis of RNA synthesis, cells growing exponentially are found to incorporate most of the added precursor into stable RNA, mainly ribosomal. The amount of cytoplasmic mRNA synthesized is only a small part of the total RNA, but radioactivity in cytoplasmic heterodisperse RNA is differentially increased during incubation of the cells in 0.05 μg/ml of actinomycin D. An investigation of the hybridization of cytoplasmic RNA with DNA showed that this is and will be a useful method in the characterization of mRNA molecules in these cells. The results are discussed as they relate to further investigation of cytoplasmic RNA. © 1969.