Involvement of p300 in TGF-beta/Smad-pathway-mediated alpha2(I) collagen expression in mouse mesangial cells.
BACKGROUND
Transforming growth factor beta 1 (TGF-beta1) induces alpha2(I) collagen gene (COL1A2) expression in mesangial cells through physical and functional cooperation of Smad proteins and Sp1. A transcriptional coactivator, p300, is also suggested to play an important role in TGF-beta1/Smad signal transduction. However, the role of p300 in TGF-beta1/Smad-pathway-mediated transcriptional activation of the COL1A2 gene in mesangial cells is still obscure.


METHODS
Endogenous p300 expression and its modulation by TGF-beta1 were evaluated by Western blotting and immunofluorescence. The physical interaction of p300 with Smad2/3 was examined by immunoprecipitation followed by Western blotting. The functional role of p300 in TGF-beta1/Smad-pathway-mediated COL1A2 transcription was investigated in cotransfection experiments using a COL1A2 promoter-luciferase reporter gene construct and p300 expression plasmids.


RESULTS
TGF-beta1 induced COL1A2 gene expression in cultured mouse mesangial cells which was blocked by overexpression of inhibitory Smad7. In addition, TGF-beta1-induced nuclear export of endogenous Smad7 was observed in mouse mesangial cells. Endogenous p300 was expressed in the nucleus of the cells. TGF-beta1 induced interaction of endogenous p300 with Smad2/3, and a dominant negative construct of p300 inhibited the TGF-beta1-induced COL1A2 expression in cultured mouse mesangial cells.


CONCLUSIONS
p300 may be involved in TGF-beta1/Smad-pathway-mediated type I collagen gene transcription in mouse mesangial cells. Our findings would reveal a molecular basis of TGF-beta1-induced type I collagen gene transcription in mouse mesangial cells.
Kanamaru
Yutaka
Y
Division of Nephrology, Department of Internal Medicine, Juntendo University School of Medicine, Tokyo, Japan.
Nakao
Atsuhito
A
Tanaka
Yuichi
Y
Inagaki
Yutaka
Y
Ushio
Hiroko
H
Shirato
Isao
I
Horikoshi
Satoshi
S
Okumura
Ko
K
Ogawa
Hideoki
H
Tomino
Yasuhiko
Y
D000818:Animals; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis* / Q000235:genetics; D024042:Collagen Type I; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D050881:E1A-Associated p300 Protein; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005799:Genes, Dominant; D017930:Genes, Reporter; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051906:Smad7 Protein; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology
D024042:Collagen Type I; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051906:Smad7 Protein; C497807:Smad7 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D003094:Collagen; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse