Functional analysis of the rod photoreceptor cGMP phosphodiesterase alpha-subunit gene promoter: Nrl and Crx are required for full transcriptional activity.
To understand the factors controlling expression of the cGMP phosphodiesterase type 6 (PDE6) genes, we have characterized the promoter of the human PDE6A gene that encodes the catalytic alpha-subunit. In vivo DNase I hypersensitivity assays revealed two sites immediately upstream of the PDE6A core promoter region. Transient transfection assay in Y79 cells of constructs containing varying lengths of the promoter region showed a decrease in promoter activity with increasing length. The most active segment contained a 177-bp upstream sequence including apparent Crx and Nrl transcription factor binding sites. Both Crx and Nrl transactivated the PDE6A promoter in HEK293 cells and showed a >100-fold increase when coexpressed. Coexpression of a dominant negative inhibitor of Nrl abolished Nrl transactivation but had no effect on Crx. DNase I footprinting assays identified three potential Crx binding sites within a 55-bp segment beginning 29 bp upstream of the transcription start point. Mutation of two of these sites reduced reporter gene activity by as much as 69%. Gel shifts showed that all three Crx sites required a TAAT sequence for efficient binding. Consistent with a requirement for Crx and Nrl in Pde6a promoter activity, Pde6a mRNA is reduced by 87% in the retina of Crx(-/-) mice and is undetectable in Nrl(-/-) mice at postnatal day 10. These results establish that both Nrl and Crx are required for full transcriptional activity of the PDE6A gene.
Department of Physiological Optics, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, 924 18th Street S., Birmingham, AL 35294, USA. pittler@uab.edu
Steven J
SJ
Pittler
Youwen
Y
Zhang
Shiming
S
Chen
Alan J
AJ
Mears
Donald J
DJ
Zack
Zhiyong
Z
Ren
Prabodh K
PK
Swain
Suxia
S
Yao
Anand
A
Swaroop
J Brandon
JB
White
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry*; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D002130:Calcium Phosphates / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005136:Eye Proteins / Q000502:physiology*; D005799:Genes, Dominant; D005982:Glutathione Transferase / Q000378:metabolism; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012160:Retina / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000201:enzymology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D001616:beta-Galactosidase / Q000378:metabolism
D050976:Basic-Leucine Zipper Transcription Factors; D002130:Calcium Phosphates; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; C490037:NRL protein, human; C084884:Nrl protein, mouse; D015534:Trans-Activators; C109288:cone rod homeobox protein; D004247:DNA; C020243:calcium phosphate; D008156:Luciferases; D005982:Glutathione Transferase; D003850:Deoxyribonuclease I; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C410522:PDE6A protein, human; C498747:Pde6a protein, mouse; D001616:beta-Galactosidase