title: QRX, a novel homeobox gene, modulates photoreceptor gene expression.
abstract: A novel paired-like homeobox gene, designated as Qrx, was identified by a yeast one-hybrid screen using the bovine Rhodopsin promoter Ret-1 DNA regulatory element as bait. Qrx is preferentially expressed in both the outer and inner nuclear layers of the retina. Its homeodomain is nearly identical to that of Rx/Rax, a transcription factor that is essential for eye development, but it shares only limited homology elsewhere. Although Qrx and Rx/Rax show similar DNA binding properties in vitro, the two proteins demonstrate distinct target selectivity and functional behavior in promoter activity assays. QRX synergistically increases the transactivating function of the photoreceptor transcription factors Crx and NRL and it physically interacts with CRX. Qrx is present in the bovine and human genomes, but appears to be absent from the mouse genome. Nonetheless, a 5.8 kb upstream region of human QRX is capable of directing expression in presumptive photoreceptor precursor cells in transgenic mice. These results indicate that Qrx may be involved in modulating photoreceptor gene expression. In addition, the finding of rare heterozygous QRX sequence changes in three individuals with retinal degeneration raises the possibility that QRX may be involved in disease pathogenesis.
authors.affiliation: McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Qing-liang
authors.initials: QL
authors.lastname: Wang
authors.forename: Shiming
authors.initials: S
authors.lastname: Chen
authors.forename: Noriko
authors.initials: N
authors.lastname: Esumi
authors.forename: Prabodh K
authors.initials: PK
authors.lastname: Swain
authors.forename: Heidi S
authors.initials: HS
authors.lastname: Haines
authors.forename: Guanghua
authors.initials: G
authors.lastname: Peng
authors.forename: B Michele
authors.initials: BM
authors.lastname: Melia
authors.forename: Iain
authors.initials: I
authors.lastname: McIntosh
authors.forename: John R
authors.initials: JR
authors.lastname: Heckenlively
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Jacobson
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Stone
authors.forename: Anand
authors.initials: A
authors.lastname: Swaroop
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Zack
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D002417:Cattle; D002874:Chromosome Mapping; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D020756:Coatomer Protein / Q000235:genetics; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020218:Response Elements / Q000235:genetics; D012164:Retinal Diseases / Q000235:genetics; D012243:Rhodopsin / Q000235:genetics*; D016415:Sequence Alignment; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D020756:Coatomer Protein; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; C084884:Nrl protein, mouse; C111251:Rx protein, vertebrate; D015534:Trans-Activators; D014157:Transcription Factors; C109288:cone rod homeobox protein; D012243:Rhodopsin