The αA-crystallin gene: Conserved features of the 5′-flanking regions in human, mouse, and chicken

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Abstract
Approximately 2 kb of 5′-flanking sequences of the lens-specific αA-crystallin genes from human and mouse are presented and compared with similar regions of the chicken gene. A repetitive element was found approximately 1 kb upstream from the coding sequences of the αA-crystallin gene in all three species (Alu in human, B2 in mouse, and CR1 in chicken), suggesting that they may have an important functional or structural role. Despite the ability of αA-crystallin promoters to function across species, dot matrix analyses show only limited similarity among the 600 bp 5′ to the structural genes of these three species. The human 5′-flanking sequence is more similar to that of the mouse and chicken than the mouse and chicken are to each other. Numerous short sequences (8–13 bp) are common to all three genes but are distributed differently in each species. The locations and conservation of these sequence motifs suggest functional roles, possibly ascis-regulatory elements of transcription. One motif is similar to the αA-CRYBP1 binding site implicated earlier in the transcriptional regulation of the mouse αA-crystallin gene, and other motifs correspond to sites previously mapped by methylation interference studies in the mouse αA-crystallin promoter. The modular arrangement of conserved sequence motifs is consistent with evolutionary changes occurring at the level of gene regulation.