Genomic organization of the human alpha 3 integrin subunit gene

The alpha 3 beta 1 integrin is a receptor for various laminin isoforms and plays an important role in the maintenance of tissue integrity. We have characterized the genomic structure of the complete gene for the human alpha 3 integrin subunit. The gene contains 26 exons spanning a region of 36.3 kb of genomic DNA. Its structure closely resembles that of alpha 6, another of the three integrin alpha-subunits that are part of laminin receptors, except that it lacks the corresponding exon 5A, which encodes an X1 region in the extracellular domain of alpha 6. However, the alpha 3 gene contains the equivalent of an exon 5B for an X2-like region, which in alpha 6 and alpha 7 is present only in certain tissue-specific alternative transcripts. The two A and B cytoplasmic variants of alpha 3, which are common to the three laminin receptor integrin alpha-subunits, are encoded by separate exons.