A mouse immunoglobulin heavy chain deletion mutant: isolation of a cDNA clone and sequence analysis of the mRNA.

The mouse cell line IF2 secretes an immunoglobulin heavy chain lacking the CH1 domain. We have isolated and characterised a recombinant plasmid containing cDNA copies of the IF2 mutant mRNA. The cloned sequence extends from the nucleotides coding for amino acid 96 in the variable region through 100 nucleotides of untranslated region at the 3' end. The sequence of the cDNA insert reveals no discontinuity at the variable-hinge region junction, the site of the CH1 deletion. Experiments employing direct priming on the poly(A) tail of the IF2 heavy chain mRNA suggest that the 3' end of the cDNA clone (sequence C-C-C-T-G-C) is also the 3' end of the mRNA.