Involvement of retinoic acid/retinoid receptors in the regulation of murine alphaB-crystallin/small heat shock protein gene expression in the lens.
Crystallins are a diverse group of abundant soluble proteins that are responsible for the refractive properties of the transparent eye lens. We showed previously that Pax-6 can activate the alphaB-crystallin/small heat shock protein promoter via the lens-specific regulatory regions LSR1 (-147/-118) and LSR2 (-78/-46). Here we demonstrate that retinoic acid can induce the accumulation of alphaB-crystallin in N/N1003A lens cells and that retinoic acid receptor heterodimers (retinoic acid receptor/retinoid X receptor; RAR/RXR) can transactivate LSR1 and LSR2 in cotransfection experiments. DNase I footprinting experiments demonstrated that purified RAR/RXR heterodimers will occupy sequences resembling retinoic acid response elements within LSR1 and LSR2. Electrophoretic mobility shift assays using antibodies indicated that LSR1 and LSR2 can interact with endogenous RAR/RXR complexes in extracts of cultured lens cells. Pax-6 and RAR/RXR together had an additive effect on the activation of alphaB-promoter in the transfected lens cells. Thus, the alphaB-crystallin gene is activated by Pax-6 and retinoic acid receptors, making these transcription factors examples of proteins that have critical roles in early development as well as in the expression of proteins characterizing terminal differentiation.
Gopal-Srivastava
R
R
Laboratory of Molecular and Developmental Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892-2730, USA.
Cvekl
A
A
Piatigorsky
J
J
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D003459:Crystallins / Q000235:genetics*; D018076:DNA, Complementary; D005786:Gene Expression Regulation / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000235:genetics*; D007908:Lens, Crystalline / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012333:RNA, Messenger / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000502:physiology*; D014162:Transfection; D014212:Tretinoin / Q000502:physiology*
D003459:Crystallins; D018076:DNA, Complementary; D006360:Heat-Shock Proteins; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D014212:Tretinoin