Structure of the human immunoglobulin C epsilon 2 gene, a truncated pseudogene: implications for its evolutionary origin.
Cloning of the overlapping DNA fragments together with Southern hybridization experiments showed the organization of the human C epsilon and C alpha gene cluster as 5'-C epsilon 2-14 kilobases-C alpha 1----C epsilon 1-13 kilobases-C alpha 2-3'. Comparison of the nucleotide sequences of the C epsilon 1 and C epsilon 2 genes revealed that four deletions have taken place in the C epsilon 2 gene and its flanking regions. The three deleted regions in the 5' side of the C epsilon 2 gene are partially filled with shorter inserted sequences. One of them has removed the CH1 and CH2 exons and a portion of the epsilon switch (S epsilon) region. The S epsilon region and the CH4 exon still retain the functional structures, whereas the CH3 exon has been inactivated by deleting its 5' intervening sequence necessary for splicing. The tetranucleotide T-G-G-G (or T-G-G-C), which is usually found in close proximity of the class-switch recombination sites in mouse myelomas, is located 5' to the three deletion sites. The results imply that the mechanism responsible for the heavy chain class-switch recombination might be relevant to the evolutionary mechanism of creation of the truncated C epsilon 2 gene. The other deletion in the 3' flanking region of the C epsilon 2 gene may be due to slipped mispairing of the short direct repeat (C-C-C-C-C) at both ends.
D001483:Base Sequence; D005075:Biological Evolution; D002872:Chromosome Deletion; D005796:Genes; D008040:Genetic Linkage; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007137:Immunoglobulin alpha-Chains / Q000235:genetics; D007139:Immunoglobulin epsilon-Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000235:genetics*; D011995:Recombination, Genetic
D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007137:Immunoglobulin alpha-Chains; D007139:Immunoglobulin epsilon-Chains; D007136:Immunoglobulins