Complete structure of the alpha B-crystallin gene: conservation of the exon-intron distribution in the two nonlinked alpha-crystallin genes.

Abstract

We isolated bovine complementary DNA clones for the .alpha.A- and .alpha.B-crystallin subunits. The .alpha.B cDNA clone was used to isolate an .alpha.B-crystallin gene. This gene, derived from hamster, occurs as a single copy in the genome and is 3.2 kilobases long. The coding sequences are spread on three exons with a total length of 709 nucleotides. The exon-intron distribution of the hamster .alpha.B-crystallin gene is similar to that of the .alpha.A-crystallin gene except for the 69 nucleotides that sepcify the 23 "insert" residues of the .alpha.AIns chain by means of differential splicing. The 3'' noncoding region of the .alpha.B mRNA (140 bases), which is short compared with the .alpha.A mRNA (520 bases), shows a remarkable homology between calf and hamster. Both .alpha.-crystallin cDNA clones have been used to assign the chromosomal location of the corresponding human genes with the aid of somatic cell hybrids. It is shown that the single-copy .alpha.A- and .alpha.B-crystallin genes are located on different chromosomes.