Region of immunoglobulin light-chain mRNA transcribed into complementary DNA by RNA-dependent DNA polymerase of avian myeloblastosis virus.

The mRNA coding for a kappa-type immunoglobulin light (L)-chain and its complementary DNA (cDNA) hybridize with a Crt1/2 of 2.6 x 10(-4) moles of ribonucleotide x liter-1 x sec, forming well-matched duplexes (melting temperature Tm equals 89 degrees). The molecular weight of the cDNA is about 280,000 (840 nucleotides) as determined by alkaline sucrose gradient centrifugation and from the extent of protection of the mRNA by the cDNA from ribonuclease digestion. The cDNA anneals with kappa-type mRNAs of the same and different subgroups with comparable Crt1/2 values, but not with a lambda-type mRNA. Thus, one kappa-type cDNA can be used to quantify the mRNAs coding for all kappa-type L-chains. The values of cDNA hybridized at saturation with various kappa-type mRNAs indicate that: (1) the cDNA is complementary to the entire constant region and to about half of the variable (V)-region; (2) V-regions of similar amino-acid sequence are coded by a similar nucleotide sequence; (3) the nucleic acid probe to one V-region may anneal and quantify V-region genes of members of the same subgroup.