Comparison of immunoglobulin chains made in ascites extract and reticulocyte lysate programmed with mRNA from four mouse myelomas

Abstract

To learn more about the cell-free synthesis of immunoglobulin (Ig) chains, the translation of mRNA from microsomes of four murine plasma cell tumors (myelomas) has been compared in a supplemented Krebs II ascites cell extract and in a rabbit reticulocyte lysate. 1. (i) In the ascites system, translation of Ig light chain mRNAs was enhanced by addition of 18-S rRNA, ascites tRNA and KCl concentrations higher than the optimum for total amino acid incorporation. Reticulocyte initiation factors strongly stimulated translation of exogenous and endogenous mRNAs. The background of endogenous incorporation was not eliminated by preincubation of the extract. 2. (ii) Messenger RNA from each of the myelomas directed synthesis predominantly of light chains and their presumptive precursors, P chains, in the ascites system. The P chains ranged in size from 1300 to 2200 daltons larger than the corresponding L chains. In response to mRNA from a particular tumor, P chains synthesized in the ascites extract and in the reticulocyte lysate (and in a wheat germ system) were indistinguishable in size. 3. (iii) Small amounts of large polypeptides serologically related to α and γ heavy chains were made in the ascites system and large amounts of an α chain related product were made in the reticulocyte system, probably in a precursor form.