Purification of Immunoglobulin Light Chain Messenger RNA by Immunoprecipitation from Mouse Myeloma Tumor, MOPC-31C1

Polysomes producing IgGl(kappa) myeloma protein were specifically selected by an immunoprecipitation method, and immunoglobulin light chain mRNA was purified from the precipitated polysomes. The purified mRNA migrated predominantly as a single band and the molecular weight of this mRNA was calculated to be 410.000 by polyacrylamide gel electrophoresis in 98% formamide. A protein possessing a molecular weight of 25,000, which is the size of the light chain precursor, was synthesized as a major product of translation in a wheat germ cell-free system. DNA complementary to the mRNA (cDNA) was prepared with avian myeloblastosis virus RNA-dependent DNA polymerase. This cDNA had an average size of 8.3S as determined by sedimentation through an alkaline sucrose gradient. Using this cDNA, Crt 1/2 values of template RNA and RNA from various preparations were calculated from the results of molecular hybridization. The relative content of the mRNA increased 4,4-fold during the immunoprecipitation of polysomes.