Lens-specific gene recruitment of zeta-crystallin through Pax6, Nrl-Maf, and brain suppressor sites.
Zeta-Crystallin is a taxon-specific crystallin, an enzyme which has undergone direct gene recruitment as a structural component of the guinea pig lens through a Pax6-dependent mechanism. Tissue specificity arises through a combination of effects involving three sites in the lens promoter. The Pax6 site (ZPE) itself shows specificity for an isoform of Pax6 preferentially expressed in lens cells. High-level expression of the promoter requires a second site, identical to an alphaCE2 site or half Maf response element (MARE), adjacent to the Pax6 site. A promoter fragment containing Pax6 and MARE sites gives lens-preferred induction of a heterologous promoter. Complexes binding the MARE in lens nuclear extracts are antigenically related to Nrl, and cotransfection with Nrl elevates zeta-crystallin promoter activity in lens cells. A truncated zeta promoter containing Nrl-MARE and Pax6 sites has a high level of expression in lens cells in transgenic mice but is also active in the brain. Suppression of the promoter in the brain requires sequences between -498 and -385, and a site in this region forms specific complexes in brain extract. A three-level model for lens-specific Pax6-dependent expression and gene recruitment is suggested: (i) binding of a specific isoform of Pax6; (ii) augmentation of expression through binding of Nrl or a related factor; and (iii) suppression of promoter activity in the central nervous system by an upstream negative element in the brain but not in the lens.
Sharon-Friling
R
R
Section on Molecular Structure and Function, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Richardson
J
J
Sperbeck
S
S
Lee
D
D
Rauchman
M
M
Maas
R
R
Swaroop
A
A
Wistow
G
G
D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D002478:Cells, Cultured; D016384:Consensus Sequence; D003459:Crystallins / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D018398:Homeodomain Proteins; D007908:Lens, Crystalline / Q000378:metabolism*; D016350:Leucine Zippers; D050977:Maf Transcription Factors; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011817:Rabbits; D012097:Repressor Proteins; D014157:Transcription Factors / Q000378:metabolism*
D050976:Basic-Leucine Zipper Transcription Factors; D003459:Crystallins; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; C111440:L-MAF protein, Gallus gallus; D050977:Maf Transcription Factors; C084884:Nrl protein, mouse; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D012097:Repressor Proteins; D014157:Transcription Factors