Genetic polymorphism and exon changes of the constant regions of the human T-cell rearranging gene gamma.

The genomic nucleotide sequences of the constant-region (C) genes of the human T-cell rearranging gene gamma are given. These sequences show considerable allelic and nonallelic variation. Allelic variants exist at both C gamma 1 and C gamma 2 loci in coding regions (as well as in restriction enzyme sites). Both C gamma genes are in the same transcriptional orientation. Moreover, the organization of the nonallelic C gamma genes reveals some interesting features: the C gamma 1 gene, like the mouse C gamma gene, has three exons, whereas the C gamma 2 gene has four exons, including a duplicated second exon that would create a putative protein with an enlarged constant region. However, these two duplicated exons in C gamma 2 have lost the cysteine residue that is thought to be involved in the interchain disulfide bridge.