THE INVOLUCRIN GENES OF THE MOUSE AND THE RAT - STUDY OF THEIR SHAREDREPEATS

The involucrin genes of the mouse (Mus musculus) and the rat (Rattus n orvegicus) have been cloned and sequenced. The coding region of each g ene contains, at site P, a segment of repeats homologous to that of ot her nonanthropoid mammals. In contrast to the repeats of species belon ging to different mammalian orders, many individual repeats of the mou se and the rat can be matched. Both before and after the divergence of the two species, these repeats have been the site of systematic alter ations in nucleotide sequence. One of the alterations is the correctio n of nucleotides of one repeat by those of another. Corrected nucleoti des may be closely linked to flanking nucleotides that are uncorrected ; the systematic correction process therefore appears to be due to gen e conversion. There is a stretch of 18 reiterated CAGs in the segment of repeats of the Mus gene; most of these reiterations were introduced recently, supporting the idea that the gene was generated originally from poly CAG. An antiserum to a synthetic peptide encoded by the segm ent of repeats of the Mus gene reveals differentiation-specific expres sion of the gene in the epidermis.