Different size of the product of the 14S light chain mRNA translated in vitro and in amphibian oocytes.

When purified 14S mRNA for light chain of immunoglobulin is translated in a reticulocyte lysate and in Xenopus oocytes, two major differences are observed: (1) In the lysate 14S RNA competes efficiently with endogenous mRNA whereas in the oocyte it is translated without reducing the synthesis of endogenous proteins. (2) The translation product of 14S light chain mRNA in the lysate is a protein about 20 amino acids longer than light chain whereas in the oocyte it is a chain of the exact size of authentic secreted light chain. This difference can be explained if 14S mRNA codes for a precursor protein, which is not cleaved in the lysate but can be efficiently converted into light chain in the oocytes.

Enzymatic synthesis of DNA complementary to purified 14S messenger RNA of immunoglobulin light chain.

The 14S messenger RNA, which contains poly(adenylic acid), of MOPC 41 (mouse plasmocytoma) immunoglobulin light chain, purified to a single peak as shown by polyacrylamide gel electrophoresis, was used to synthesize complementary DNA with the RNA-dependent DNA polymerase of avian myeloblastosis virus. DNA synthesis is entirely dependent on added RNA template and oligo(dT) primer. Both the size and the concentration of the primer affect the reaction.

Purification of 14S messenger RNA of immunoglobulin light chain that codes for a possible light-chain precursor.

Polysomes released from microsomes of MOPC 41 mouse myeloma were used to prepare a poly(A)-containing fraction of RNA by chromatography on poly-(dT)-cellulose. From that fraction, a 14S RNA species was purified to a single peak by successive sucrose gradient centrifugations, followed by acrylamide gel electrophoresis. The RNA has an apparent molecular weight of 380,000 (1100 nucleotides), as estimated from the electrophoretic analyses.

Template activity of RNA from antibody-producing tissues.

An RNA fraction, which represents a small percentage of cellular RNA and which has the characteristics of nuclear messenger RNA, has been isolated from the spleen and lymph nodes of immunized rats by successive phenol extractions of these tissues at increasing temperatures. This fraction increased the amount of protein synthesized in a cell-free extract of Escherichia coli as much as 35 times and directed the synthesis of proteins different from those of E. coli.