Organization of the sequences flanking immunoglobulin heavy chain genes and their role in class switching

Abstract

We have used heteroduplex analysis to investigate the sequences surrounding the germline Cγ1 and Cγ3 genes, and to compare them with those surrounding the Cμ gene. We detected an inverted pseudogene 5′ to the Cγ3 gene and 50-65% homologous to it. A 400 bp region of the Cγ1 and Cγ3 3′ flanking sequences was conserved as strongly as the genes (65-80%), suggesting it may have a specific function. The sequences 5′ to the Cγ1 and Cγ3 genes and possibly also the Cμ gene are composed of tandem partially homologous repeats of a similar 250 bp unit, arranged in the case of the Cγ1 gene, in 2-5 kb blocks of alternating orientation. These repeats comprised over 13 kb of the spacer region separating the..