Comparative analysis of the zeta-crystallin/quinone reductase gene in guinea pig and mouse

zeta-Crystallin is a novel nicotinamide adenine dinucleotidephosphate:quinone reductase, present at enzymatic levels in various tissuesof different species, which is highly expressed in the lens of somehystricomorph rodents and camelids. We report here the complementary DNA(cDNA) cloning of zeta-crystallin from liver libraries in guinea pig (Caviaporcellus), where zeta-crystallin is highly expressed in the lens, and inthe laboratory mouse (Mus musculus), where expression in the lens occursonly at enzymatic levels. A 5' untranslated sequence different from the onepreviously reported for the guinea pig lens cDNA was found in these clones.We also report the isolation of genomic clones including the completeguinea pig zeta-crystallin gene and the 5' region of this gene in mouse.These results show the presence of two promoters in the guinea pigzeta-crystallin gene, one responsible for expression at enzymatic levelsand the other responsible for the high expression in the lens. The guineapig lens promoter is not present in the mouse gene. This is the firstexample in which the recruitment of an enzyme as a lens crystallin can beexplained by the acquisition of an alternative lens- specific promoter.