1: Mol Vis. 2001 Jan 2;7:1-5. 

Quantitation of PAX6 and PAX6(5a) transcript levels in adult human lens, cornea,
and monkey retina.

Zhang W, Cveklova K, Oppermann B, Kantorow M, Cvekl A.

Department of Biology, West Virginia University, Morgantown, WV, USA.

PURPOSE: PAX6 is a critical regulator of the developing lens, other ocular
tissues, central nervous system, and pancreas. There are two alternatively
spliced forms of the protein, PAX6 and PAX6(5a), that may have different
regulatory functions. This study was designed to determine the amounts of PAX6
and PAX6(5a) transcripts present in adult human lens epithelium and fibers,
human cornea and monkey retina. METHODS: PAX6 and PAX6(5a) transcript levels
were monitored in microdissected lens epithelia, lens fibers, whole lens,
cornea, and retina by competitive RT-PCR. The levels of TBP/TFIID were examined
in adult human lens epithelium and fibers as control. RESULTS: PAX6 and PAX6(5a)
were expressed at equal levels in lens epithelium and fibers. Ninety-five times
more PAX6 transcripts were detected in the epithelial cells than in the fibers.
Adult human cornea and monkey retina expressed less PAX6/PAX6(5a) than lens
epithelium but more than lens fibers. Correspondingly, 40 fold higher levels of
TBP transcripts were detected in lens epithelium than fibers, suggesting reduced
overall expression of transcription factors in the adult lens fibers.
CONCLUSIONS: The presence of PAX6 and PAX6(5a) messages and proteins in adult
lens epithelium suggest functions for both forms of PAX6 in the growth and
maintenance of the adult human lens. The reduced levels of both forms of PAX6 in
the lens fibers suggest down regulation of this gene during differentiation of
epithelia into fibers. The lower level of TBP expression in lens fibers also
suggests reduced transcriptional competence of adult lens fibers.

PMID: 11172136 [PubMed - indexed for MEDLINE]


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2: Invest Ophthalmol Vis Sci. 1999 Jun;40(7):1343-50. 

Pax-6 interactions with TATA-box-binding protein and retinoblastoma protein.

Cvekl A, Kashanchi F, Brady JN, Piatigorsky J.

Laboratory of Molecular and Developmental Biology, National Eye Institute,
National Institutes of Health, Bethesda, Maryland 20892-2730, USA.

PURPOSE: To identify proteins that physically interact with Pax-6, a paired
domain- and homeodomain (HD)-containing transcription factor that is a key
regulator of eye development. METHODS: Protein-protein interactions involving
Pax-6, TATA-box-binding protein (TPB), and retinoblastoma protein were studied
using affinity chromatography with Pax-6 as ligand, glutathione-S-transferase
(GST) pull-down assays, and immunoprecipitations. RESULTS: The authors have
shown that Pax-6 is a sequence-specific activator of many crystallin genes, all
containing a TATA box, in the lens. Others have shown that lens fiber cell
differentiation, characterized by temporally and spatially regulated crystallin
gene expression, depends on retinoblastoma protein. In the present study it was
shown that Pax-6 interacted with the TBP, the DNA-binding subunit of general
transcription complex TFIID. GST pull-down assays indicated that this
interaction was mediated by the Pax-6 HD, with a substantial role for its
N-terminal arm and first two alpha-helices. The experiments also indicated a
binding role for the C-terminal-activation domain of the protein. In addition,
the present study showed that the HD of Pax-6 interacted with retinoblastoma
protein. Immunoprecipitation experiments confirmed retinoblastoma protein/Pax-6
complexes in lens nuclear extracts. CONCLUSIONS: Blending the present results
with those in the literature suggests that Pax-6 and retinoblastoma protein
participate in overlapping regulatory pathways controlling epithelial cell
division, fiber cell elongation, and crystallin gene expression during lens
development.

PMID: 10359315 [PubMed - indexed for MEDLINE]


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