Missense mutation at the C-terminus of PAX6 negatively modulates homeodomain function.
PAX6 is essential for ocular morphogenesis. Mutations in the PAX6 gene produce various phenotypes, including aniridia, Peters' anomaly, foveal hypoplasia, autosomal dominant keratitis and congenital cataracts. PAX6 functions as a transcription factor and has two DNA binding domains (a paired domain and a homeodomain) which are joined by a linker, and a transactivation domain enriched in proline, serine and threonine (PST) at the C-terminus. The mechanism of PAX6 function is not clearly understood, and few target genes in vertebrates have been identified. We examined disease-causing missense mutations in the PST domain to understand how they affect the function of PAX6. Upon examining the DNA samples of aniridia patients, we identified three missense mutations in the PST domain: P375Q (a novel mutation) and the previously reported Q422R and X423L mutations. On the basis of functional analysis, the P375Q mutant appears to have a normal transactivation activity but lower DNA binding through the paired domain than the wild-type. The Q422R mutation resulted in the loss of DNA binding ability of the PAX6 homeodomain. Substitution analyses of the C-terminal amino acid (codon 422) indicated that an amino acid at codon 422 is required for DNA binding of the homeodomain of intact PAX6 and that the polarity and charge of the side-chain of the terminal amino acid influence this binding.
Singh
S
S
Department of Biochemistry and Molecular Biology, The University of Texas M.D. Anderson Cancer Center, Box 117, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Chao
L Y
LY
Mishra
R
R
Davies
J
J
Saunders
G F
GF
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D015783:Aniridia / Q000235:genetics*; D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D015533:Transcriptional Activation; D014162:Transfection; D001616:beta-Galactosidase / Q000378:metabolism
D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D009838:Oligodeoxyribonucleotides; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D011994:Recombinant Proteins; D012097:Repressor Proteins; D008156:Luciferases; D001616:beta-Galactosidase