The structure, expression, and evolution of the crystallin genes of vertebrates and invertebrates are being studied. The following advances have been made. Pax-6 activates the chicken and mouse ALPHA-crystallin promoter and the chicken delta1-crystallin enhancer. The chicken alphaA promoter contains a composite element that suppresses activity in fibroblas by binding USF and AP-1 proteins (JunD and Fra2) and activates promoter activity in lens by binding USF and CREB CREM proteins. USF also acts as a negative regulator of the chicken alphaA promoter by binding to another, downstream element. USF also binds to the deltaEF1 site of the chicken delta1-crystallin enhancer, where it probably contributes to the activation of this gene. CREB CREM cooperates with alphaA-CRYBP1 and Pax-6 to activate the mouse alphaA promoter in lens cells. Binding studies suggest that HSF may also be involved in chicken alphaA and mouse gammaF promoter activity. Expression of the mouse alphaB-crystallin gene in different tissues utilizes both shared and tissue-specific control elements the exact pattern being called its """"""""regulatory tissue print."""""""" Elements for lens-specific expression have been narrowed to positions -101/+30 in the chicken betaB1 gene and -143/+22 in the chicken betaBA3/A1 gene in transgenic mouse experiments. alphaA, alphaB and betaB2 were shown to be able to autophosphorylate, raising the possibility that they are involved i a signal transduction pathway. Close linkage was found for chicken betaB1 and betaA4, and evidence was obtained indicating that mammalian betaB2 is expressed in nonlens cells. A CR1 element was found in the intergenic spacer of duck delta-crystallin; the duck delta1 and delta2 polypeptides were shown to interact cooperatively to modulate argininosuccinate lyase activity of the tetramer. The jellyfish J3-crystallin gene has been cloned and shown to contain at least six introns.
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