Cell-free translation of immunoglobulin messenger RNA from MOPC-315 plasmacytoma and MOPC-315 NP-1, a variant synthesizing only heavy chain

MOPC-315 plasmacytoma cells produce intact immunoglobulin (IgA) molecules; the variant MOPC-315 NP-1 plasmacytoma synthesizes the heavy chain only. The heavy chains from MOPC-315 and MOPC-315 NP-1 have nearly identical tryptic peptide patterns. Total poly(A)-containing mRNA was isolated and partially purified from MOPC-315 and MOPC-315 NP-1 plasmacytomas. MOPC-315 fractions directed the cell-free synthesis of both the heavy- and light-chain precursors of the MOPC-315 IgA protein. One of the MOPC-315 NP-1 fractions tested had the capacity to direct the synthesis of the MOPC-315 IgA heavy chain. Analysis of the cell-free products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by immunoprecipitation demonstrated that no translatable poly(A)-containing light-chain mRNA could be extracted from the MOPC-315 NP-1 variant plasmacytoma.