In vitro synthesis of DNA complementary to mRNA derived from a light chain-producing myeloma tumour

Functional cDNA expression cloning: pushing it to the limit

The 1970s and the following decade are the era of the birth and early development of recombinant DNA technologies, which have entirely revolutionized the modern life science by providing tools that enable us to know the structures of genes and genomes and to dissect their components and understand their functions at the molecular and submolecular levels. One major objective of the life sciences is to achieve molecular and chemical understandings of the functions of genes and their encoded proteins, which are responsible for the manifestation of all biological phenomena in organisms. In the early 1980s, I developed, together with Paul Berg, a new technique that enables the cloning of full-length complementary DNAs (cDNAs) on the basis of their functional expression in a given cell of interest. I review the development, application and future implications in the life sciences of this gene-cloning technique.

Study of markers of human erythroid differentiation in hybrid cells

Somatic cell hybrids exhibiting co-expression of the globin genes of two species were generated by fusion of mouse erythroleukemia cells with Chinese hamster or human marrow erythroid cells. In contrast, extinction of the mouse globin genes occurred in hybrids formed between the erythroleukemia cells and human fibroblasts. Direct detection of the human globin genes in human X mouse fibroblast hybrids was achieved by annealing of DNA from these cells to human globin complementary DNA. This method was developed to permit the chromosomal assignment of the human globin genes.

Synthesis of DNA complementary to the mRNAs for milk proteins by E. coli DNA polymerase I

E.Coli DNA polymerase I (Klenow subfragment) was used for the synthesis of complementary DNA with the mRNAs for rabbit milk proteins as templates. The cDNA formed, contained 200 nucleotides and represented about 20% of the mRNA template. The cDNA was hybridized specifically to the mRNA templates. The Klenow subfragment of the E.Coli DNA polymerase I was as efficient as the avian myeloblastosis virus reverse transcriptase in the synthesis of cDNA. The mean size of the cDNA fragments obtained with the Klenow enzyme proved to be 70% of the value obtained with the AMV reverse transcriptase and at least twice the value generally obtained with the complete E.Coli DNA polymerase I. The cDNA was used for the detection and the quantification of the mRNA template in various RNA fractions.

Transcription in vitro of immunoglobulin kappa light chain genes in isolated mouse myeloma nuclei and chromatin

Messenger RNA sequences for immunoglobulin kappa light chain were synthesized in vitro in isolated mouse myeloma nuclei using bound endogenous RNA polymerase (RNA nucleotidyltransferase; nucleoside triphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) and from isolated myeloma chromatin using exogenous Escherichia coli RNA polymerase. The in vitro RNA was transcribed using 5-mercuriuridine triphosphate and separated from in vivo RNA by chromatography on an agarose sulfhydryl affinity column. Template restriction is retained in vitro since synthesis of kappa chain messenger RNA, As determined by hybridization with complementary DNA, was much more efficient in nuclei and chromatin isolated from myeloma 66.2 tissue culture cells, a kappa-chain-producing cell line, than from MOPC 315 tissue culture cells, a lambda-chain-producing cell line. Transcription of kappa chain messenger RNA was 25 times more efficient in myeloma 66.2 nuclei than in myeloma 66.2 chromatin.

Characterization of light chain and light chain constant region fragment mRNAs in MPC 11 mouse myeloma cells and variants

Cultured MPC 11 mouse myeloma cells synthesize not only gamma2b heavy and kappa light chains but also a carboxyl terminal (constant region) fragment of kappa light chain. In vitro translational analysis of total cytoplasmic and microsomal RNA indicates that these cells contain RNA which directs synthesis of both a light chain precursor and a light chain fragment precursor. Variant clones which do not synthesize either heavy or light chains continue to synthesize the light chain fragment. One such "nonproducing" variant was studied in detail. It does not contain translatable mRNA for the intact light chain but does contain RNA which is translated into the light chain fragment precursor. Nucleic acid hybridization analysis with a cDNA probe specific for the constant region of kappa light chains revealed that microsomal RNA from the wild-type cell contains both 14S and a 10S species of kappa specific RNA, whereas the variant contains only the 10S species. Translational analysis of these same RNAs indicates that the 14S species codes for the light chain precursor, while the 10S RNA codes for the light chain fragment precursor.

Mouse immunoglobulin genes: studies on the reiteration frequency of light-chain genes by hybridisation procedures

The partially purified immunoglobulin light chain messenger RNA fraction from P3K (MOPC 21) mouse myeloma tissue-culture cells has been employed in hybridisation studies. Fragments of the messenger RNA were generated by alkali hydrolysis. 6-S fragments not containing poly(A) showed the characteristic biphasic hybridisation profile seen with the intact RNA fraction. 12-S and 6-S poly(A)-containing fragments, however, showed single transitions lacking the rapidly hybridising component. Complementary DNA copies of the intact messenger RNA fraction were prepared with RNA-dependent DNA polymerase and the DNA populations fractionated on acrylamide gels. Hybridisation experiments with complementary DNA fractions up to 800 bases in length showed annealing to single (or a few) genes. A rapidly hybridising component (about 200 copies) appears in the cDNA fraction containing the largest transcripts. We conclude that the kappa constant region gene and the MOPC 21 variable region gene are present as one or a few copies in the haploid genome and that the rapidly hybridising component is not due to variable region genes.

Enzymatic synthesis of solid phase-bound DNA sequences corresponding to specific mammalian genes

With oligo(dT)-cellulose as primer, RNA-dependent DNA polymerase catalyzes the synthesis of cellulose-bound DNA that is complementary to mouse globin mRNA. The resulting cellulose-bound or solid phase complementary DNA hybridizes specifically with globin mRNA and permits the recovery of intact globin mRNA. This simple technique for the synthesis of solid phase-bound complementary DNA provides an additional and convenient method for the purification of specific genetic sequences.

Organization of immunoglobulin genes: reiteration frequency of the mouse kappa chain constant region gene

Hybridization kinetic analyses with synthetic DNA indicate that there are only two to three copies of the kappa constant region gene per haploid genome. This result lends weight to the argument that the immunoglobulin light chain is encoded by more than one continuous gene sequence.

Nucleotide sequence analysis of RNA synthesized from rabbit globin complementary DNA

Rabbit globin complementary DNA made with RNA-dependent DNA polymerase (reverse transcriptase) was used as template for in vitro synthesis of (32)P-labeled RNA. The sequences of the nucleotides in most of the fragments resulting from combined ribonuclease T(1) and alkaline phosphatase digestion have been determined. Several fragments were long enough to fit uniquely with the alpha or beta globin amino-acid sequences. These data demonstrate that the cDNA was copied from globin mRNA and contained no detectable contaminants.