A homozygous a2/a2 and b4/b4 rabbit has been hyperimmunized with Mirococcus lysodeiktiu. Poly(A)-containing RNA has been isolated from the spleen and translated in vitro, and translation products have been analyzed by NaDodSOd polyacrylamide gel electrophoresis. Double-stranded cDNA has been synthesized from poly(A)-containing RNA template and inserted in the Pst I endonuclease site of plasmid pBR322 by using the oligo(dC)-oligo(dG) tailing procedure. Tetracycline-resistant ampicillin-sensitive clones containing cDNA complementary to a sc light chain mRNA have been selected by differential screening and their ability to hybridize to a spleen mRNA having the same size as a mouse Klight chain mRNA. Two clones, pRk-15 and pRk-32, have been selected to determine the nucleotide sequence of the constant and 3' untranslated regions of X light chain mRNA, by the Maxam and Gilbert partial degradation method. Comparison of homologous regions ofmouse uc chain mRNA and b4 rabbit it chain mRNA reveals 61% homology in the constant region and 59% homology in the 3' untranslated region.Serological studies ofrabbit immunoglobulins have revealed an important genetic polymorphism called allotypy (1, 2). Structures responsible for allotypic specificities have been located on constant (C) and variable (V) regions of heavy chains and on the C region oflight (L) chains (for a review, see ref.3). Genetic studies on the inheritance of allotypes have shown that these polymorphic forms segregate in a Mendelian fashion, implying that they are encoded by allelic structural genes (4).Four allotypic forms ofthe domestic rabbit K chain have been characterized (5, 6). They are designated by the symbols b4, b5, b6, and b9. The sequences ofthe CK region of b4 and b9 chains exhibit a surprising divergence; they differ by 35% of their amino acid sequences, and nine two-base substitutions and three gaps are found (7,8). Furthermore, serological analysis has shown that one heterozygous b4/b5 rabbit can express three allotypes of the b series (b4, b5, b6) (9). The extensive divergence of allelic forms of rabbit K chains and the occurrence of latent allotypes have led to the hypothesis that b allotypes in the rabbit are encoded by multiple closely linked genes regulated by a polymorphic control mechanism (8,10). Studying, at the DNA level, the gene segments coding for the rabbit b allotypes presents two main difficulties: (i) there is no rabbit myeloma cell line; (i) the extensive divergence between rabbit and mouse C sequence (44% homology at the amino acid level) makes uncertain the possibility of screening a rabbit cDNA library with a cloned mouse CK probe.Starting from hyperimmunized rabbit spleen, we have constructed cDNA clones complementary to a rabbit K chain mRNA. The sequence of the constant and 3' untranslated regions of a rabbit b4 K chain mRNA has been determined and compared to corresponding mouse sequences.
MATERIALS AND METHODSEnzymes and Chemicals. Terminal deoxynucleotidyl transferase, phage T4 polynucleotide kinase, and rest...