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B Mach

Publications and source records attributed to B Mach.

At least 217 records · Page 12Linked to original sources
PubMed1974

Estimation of the number of genes coding for the constant part of the mouse immunoglobulin kappa light chain.

As previously shown, purified 14S RNA of mouse myeloma MOPC-41 forms a single peak on sucrose gradients and gel electrophoresis and codes for a single polypeptide chain, the immunoglobulin light chain produced by the same myeloma in vivo. This 14S mRNA was used for the enzymatic synthesis of DNA (cDNA) which is complementary to the RNA template. A DNA fraction was isolated which has an average size of 300 nucleotides. Kinetic studies of the hybridization of the 14S RNA with the cDNA indicate that about 40% of the RNA consists of a single RNA sequence. From the size of the cDNA fraction and from the direction of DNA synthesis, it can be concluded that the cDNA includes the sequence complementary to the constant region of light chain mRNA. This radioactive cDNA was used for DNA.DNA reannealing experiments with unlabeled DNA from mouse liver or myeloma tumor in 3 x 10(6)-fold excess. This allowed the determination of the number of copies in the mouse genome of those sequences represented in the cDNA. The data show no significant reiteration in either liver or myeloma DNA and suggest that the gene coding for the constant part of immunoglobins is present in the haploid genome in one to five copies. Furthermore, this gene is not "amplified" in nuclear DNA of myeloma plasmocytes.

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PubMed1973

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. In a reticulocyte lysate this RNA directs the synthesis of a protein that migrates more slowly in sodium dodecylsulfate-acrylamide gels than does the light chain secreted by the same tumor. This difference in migration corresponds to a size difference appropriate for polypeptide chain about 20 amino acids longer than the light chain. The tryptic peptides of this protein correspond to those of the secreted light chain, except for the presence of two additional peptides from the product synthesized in vitro and for the absence of one light-chain peptide. The purified RNA is, therefore, the mRNA of the light chain, and it seems to code for a precursor protein slightly larger than the light chain. From the estimated size of the 14S mRNA, it appears that only 65% of the RNA is translated.

Animals↗
PubMed1973

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. The product behaves similarly to DNA during centrifugation in cesium sulfate density gradients. It is shown by hybridization that the DNA made is complementary to the purified template, light-chain mRNA. The high specific activity of the complementary DNA should make it suitable for gene-dosage experiments. According to alkaline sucrose gradient analyses, some complete complementary DNA transcripts of the 14S mRNA seem to be made. Oligo(dG) can also function as a primer for DNA synthesis, possibly by annealing to an internal cluster of cytidines in the mRNA, that correspond to the bases coding for amino-acids 119 and 120 of the MOPC 41 light chain.

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