Identification and functional analysis of the novel S179R POU1F1 mutation associated with combined pituitary hormone deficiency.
BACKGROUND
The pituitary-specific transcription factor 1 plays a key role in the development and differentiation of three pituitary cell types: somatotrophs, lactotrophs, and thyrotrophs. Several mutations of the human gene (called POU1F1) have been shown to be responsible for a phenotype of combined pituitary hormone deficiency involving GH, prolactin (PRL), and TSH.


OBJECTIVE
We have identified a novel homozygous C to G mutation in exon 4 of the POU1F1 gene (S179R) in a patient with this rare phenotype. We analyzed the functional consequences of this S179R mutation associated with a single-amino acid change in the POU-specific domain.


METHODS
Consequences of this mutation on transcriptional activities by transfection studies in alphaT3 cells, DNA binding ability by EMSA, structural properties, and nuclear accumulation of POU1F1 were investigated.


RESULTS
The transactivation capacity of this mutant was markedly decreased on the GH1, PRL, TSHbeta, and POU1F1 genes. Interestingly, this mutation abolished the functional interaction of POU1F1 on the PRL promoter with the coactivator cAMP response element-binding protein-binding protein but not with the transcription factor LIM homeodomain transcription factor 3. The S179R mutant displayed normal nuclear accumulation but a markedly decreased binding to a DNA response element in keeping with crystallographic data, suggesting that the S179R mutation might interfere with DNA binding.


CONCLUSIONS
Together with previous data, our study indicates that both DNA binding and interaction with cofactors like cAMP response element-binding protein-binding protein are critical for POU1F1 function and that functional and structural properties of abnormal POU1F1 proteins are variously influenced by the type of mutations.
Miyata
Ichiro
I
Department of Pediatrics, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Tokyo 105-8461, Japan. i-miyata@jikei.ac.jp
Vallette-Kasic
Sophie
S
Saveanu
Alexandru
A
Takeuchi
Mizuho
M
Yoshikawa
Hideki
H
Tajima
Asako
A
Tojo
Katsuyoshi
K
Reynaud
Rachel
R
Gueydan
Magali
M
Enjalbert
Alain
A
Tajima
Naoko
N
Eto
Yoshikatsu
Y
Brue
Thierry
T
D000328:Adult; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004252:DNA Mutational Analysis; D006801:Humans; D007018:Hypopituitarism / Q000235:genetics*; D008297:Male; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D010907:Pituitary Hormones / Q000172:deficiency*; D011487:Protein Conformation; D050817:Transcription Factor Pit-1 / Q000235:genetics*; D014162:Transfection
D050505:Mutant Proteins; C494187:POU1F1 protein, human; D010907:Pituitary Hormones; D050817:Transcription Factor Pit-1