Structure and expression of the scallop Omega-crystallin gene. Evidence for convergent evolution of promoter sequences.
Omega-crystallin of the scallop lens is an inactive aldehyde dehydrogenase (1A9). Here we have cloned the scallop Omega-crystallin gene. Except for an extra novel first exon, its 14-exon structure agrees well with that of mammalian aldehyde dehydrogenases 1, 2, and 6. The -2120/+63, -714/+63, and -156/+63 Omega-crystallin promoter fragments drive the luciferase reporter gene in transfected alphaTN4-1 lens cells and L929 fibroblasts but not in Cos7 cells. Putative binding sequences for cAMP-responsive element-binding protein (CREB)/Jun, alphaACRYBP1, AP-1, and PAX-6 in the Omega-crystallin promoter are surprisingly similar to the cis-elements used for lens promoter activity of the mouse and chicken alphaA-crystallin genes, which encode proteins homologous to small heat shock proteins. Site-specific mutations in the overlapping CREB/Jun and Pax-6 sites abolished activity of the Omega-crystallin promoter in transfected cells. Gel shift experiments utilizing extracts from the alphaTN4-1, L929, and Cos7 cells and the scallop stomach and oligonucleotides derived from the putative binding sites of the Omega-crystallin promoter showed complex formation. Gel shift experiments showed binding of recombinant Pax-6 and CREB to their respective sites. Our data suggest convergent evolutionary adaptations that underlie the preferential expression of crystallin genes in the lens of vertebrates and invertebrates.
Carosa
Eleonora
E
Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-2730, USA.
Kozmik
Zbynek
Z
Rall
J Edward
JE
Piatigorsky
Joram
J
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002460:Cell Line; D003459:Crystallins / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic
D003459:Crystallins