title: Interaction of retinal bZIP transcription factor NRL with Flt3-interacting zinc-finger protein Fiz1: possible role of Fiz1 as a transcriptional repressor.
abstract: NRL (neural retina leucine zipper) is a basic motif leucine zipper transcription factor of the Maf-subfamily. Multiple phosphorylated isoforms of NRL are detected specifically in rod photoreceptors. NRL regulates the expression of several rod-specific genes, including rhodopsin and cGMP phosphodiesterase beta-subunit, in synergy with other transcription factors (e.g. the homeodomain protein CRX). Missense mutations in the human NRL gene are associated with autosomal dominant retinitis pigmentosa, whereas the loss of its function leads to rodless retina in Nrl-knockout mice that exhibit enhanced S-cone function. To further elucidate the molecular mechanism(s) underlying NRL-mediated transcriptional regulation, we used yeast two-hybrid screening to isolate NRL-interacting proteins in the retina and report the identification of Flt3-interacting zinc-finger protein, Fiz1. Interaction of Fiz1 and NRL-leucine zipper was validated by GST pulldown assays and co-immunoprecipitation from bovine retinal nuclear extracts. Fiz1 suppressed NRL- but not CRX-mediated transactivation of rhodopsin promoter activity in transiently transfected CV1 cells. The mRNA and the protein for both Fiz1 and its only other known interacting protein Flt3, a receptor tyrosine kinase, are expressed in the retina. Our results indicate potential cross-talk among signaling pathways in the retina and suggest that the function of NRL is modulated by its interaction with specific repressor proteins.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA.
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Mitton
authors.forename: Prabodh K
authors.initials: PK
authors.lastname: Swain
authors.forename: Hemant
authors.initials: H
authors.lastname: Khanna
authors.forename: Mary
authors.initials: M
authors.lastname: Dowd
authors.forename: Ingrid J
authors.initials: IJ
authors.lastname: Apel
authors.forename: Anand
authors.initials: A
authors.lastname: Swaroop
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002417:Cattle; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques; D016335:Zinc Fingers; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005136:Eye Proteins; C485638:FIZ1 protein, human; C120694:Fiz1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; C490037:NRL protein, human; C084884:Nrl protein, mouse; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012243:Rhodopsin; D005982:Glutathione Transferase; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3