DO MINIGENES CODE FOR ALL FRAMEWORK SEGMENTS OF IMMUNOGLOBULIN CHAINS

Abstract

Publisher Summary This chapter discusses the hypothesis that the nucleotides coding for the FR segments are minigenes, a minigene being defined as a gene coding for a segment of a polypeptide chain, and that complete V regions are assembled somatically by the assortment of FR and CDR minigenes. The studies on mouse λ clones confirmed the hypothesis of the somatic assembly of nucleotides coding for FR4, including two residues of CDR3, residues 96–107—their J piece—to the nucleotide sequence for the rest of the V region, residues 1–95. If the nucleotides coding for FRI through almost to the end of CDR3 are already assembled in the genome, then whenever sequence differences in residues 1–95 are found between two V regions, a separate gene must exist. A minigene for a primordial FR2 segment existing in but a single or a few copies with the alternative forms having arisen by gene duplication and mutation would account completely for the data and for the finding that the other minigenes are used much less frequently.