Barrier to autointegration factor interacts with the cone-rod homeobox and represses its transactivation function.
Crx (cone-rod homeobox) is a homeodomain transcription factor implicated in regulating the expression of photoreceptor and pineal genes. To identify proteins that interact with Crx in the retina, we carried out a yeast two-hybrid screen of a retinal cDNA library. One of the identified clones encodes Baf (barrier to autointegration factor), which was previously shown to have a role in mitosis and retroviral integration. Additional biochemical assays provided supporting evidence for a Baf-Crx interaction. The Baf protein is detectable in all nuclear layers of the mouse retina, including the photoreceptors and the bipolar cells where Crx is expressed. Transient transfection assays with a rhodopsin-luciferase reporter in HEK293 cells demonstrate that overexpression of Baf represses Crx-mediated transactivation, suggesting that Baf acts as a negative regulator of Crx. Consistent with this role for Baf, an E80A mutation of CRX associated with cone-rod dystrophy has a higher than normal transactivation potency but a reduced interaction with Baf. Although our studies did not identify a causative Baf mutation in retinopathies, we suggest that Baf may contribute to the phenotype of a photoreceptor degenerative disease by modifying the activity of Crx. In view of the ubiquitous expression of Baf, we hypothesize that it may play a role in regulating tissue- or cell type-specific gene expression by interacting with homeodomain transcription factors.
Wang
Xuejiao
X
Department of Ophthalmology and Visual Sciences, Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Xu
Siqun
S
Rivolta
Carlo
C
Li
Lili Y
LY
Peng
Guang-Hua
GH
Swain
Prabodh K
PK
Sung
Ching-Hwa
CH
Swaroop
Anand
A
Berson
Eliot L
EL
Dryja
Thaddeus P
TP
Chen
Shiming
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002460:Cell Line; D003001:Cloning, Molecular; D019295:Computational Biology; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D015723:Gene Library; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D051381:Rats; D012160:Retina / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
C501959:BANF1 protein, human; C501960:Banf1 protein, mouse; C501961:Banf1 protein, rat; D017931:DNA Primers; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D015534:Trans-Activators; C109288:cone rod homeobox protein