Activin A-induced expression of PAX4 in AR42J-B13 cells involves the increase in transactivation of E47/E12.
Pax4 is a paired-homeodomain containing transcriptional factor that controls the differentiation of pancreatic beta cells. The aim of this study was to investigate the mechanism of PAX4 expression by activin A. By reporter gene analysis using AR42J-B13 cells, in which treatment with activin A induced PAX4 mRNA expression, we identified that a short sequence located approximately 1930 bp upstream of the transcriptional start site is essential for activin A induced PAX4 promoter activation. This region contains an E box and binding sites for hepatocyte nuclear factor (HNF)-1alpha. Mutation introduced in each binding site markedly reduced activin A responsiveness. It has been reported that HNF-1alpha synergizes with basic helix-loop-helix (bHLH) proteins in activating the PAX4 promoter, and we demonstrated that activin A strongly enhanced the functional activity of E47/E12 without the increase in its binding ability. In addition, suppression of E47/E12 expression in AR42J-B13 cells using siRNA oligonucleotides results in the significant decrease in the intrinsic activin A-induced PAX4 expression. Our results suggest that activin A enhances PAX4 expression by enhanced transactivation of E47/E12 proteins and might result in a cumulative transactivation of the promoter.
Kanno
Rei
R
Department of Medicine, Metabolism and Endocrinology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
Ogihara
Takeshi
T
Igarashi
Yasuhiro
Y
Tanaka
Yasushi
Y
Smith
Stuart B
SB
Kojima
Itaru
I
German
Michael S
MS
Kawamori
Ryuzo
R
Watada
Hirotaka
H
D028341:Activins / Q000494:pharmacology*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D024721:E-Box Elements; D005786:Gene Expression Regulation / Q000187:drug effects; D051538:Hepatocyte Nuclear Factor 1-alpha; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D028322:Inhibin-beta Subunits / Q000494:pharmacology*; D051761:Paired Box Transcription Factors / Q000235:genetics*; D051820:TCF Transcription Factors / Q000235:genetics*; D058125:Transcription Factor 7-Like 1 Protein; D015533:Transcriptional Activation / Q000187:drug effects*
D051538:Hepatocyte Nuclear Factor 1-alpha; D018398:Homeodomain Proteins; C491709:PAX4 protein, human; D051761:Paired Box Transcription Factors; D051820:TCF Transcription Factors; C544912:TCF7L1 protein, human; D058125:Transcription Factor 7-Like 1 Protein; C422405:activin A; D028341:Activins; D028322:Inhibin-beta Subunits