Title:The PP2A-Aβ Gene is Regulated by Multiple Transcriptional Factors Including Ets-1, SP1/SP3, and RXRα /β
Volume: 12
Issue: 8
Author(s): W. -J. Han, D. W.-C. Li, S. -J. Liu, Y. Liu, S. -P. Liang, Y. -M. Xiao, W. -B. Liu, Z. Woodward, J. Liu, X. Hu, W. -F. Hu, P. -C. Chen, J. Liu, L. Chen, M. Deng, L. Gong, X. Zhang, L. Liu, Y. Mao, H. -G. Chen, L. Zhang, S. Sun and W. Ji
Affiliation:
Keywords:
Protein phosphorylation, dephosphorylation, PP-2A, PP2A-Aβ, gene regulation, Ets, SP1, SP3,
RXRα/β, lens, retina, cataract, cancer, eukaryotic cells, cell transformation.
Abstract: Protein phosphatase-2A (PP-2A) is a major serine/threonine phosphatase abundantly expressed in
eukaryotes. PP-2A is a heterotrimer that contains a 65kD scaffold A subunit, a 36kD catalytic C subunit, and a
regulatory B subunit of variable isoforms ranging from 54-130kDs. The scaffold subunits, PP2A-Aα/β, act as
platforms for both the C and B subunits to bind, and thus are key structural components for PP-2A activity. Mutations
in both genes encoding PP2A-Aα and PP2A-Aβ lead to carcinogenesis and likely other human diseases. Our
previous work showed that the gene coding for PP2A-Aα is positively regulated by multiple transcription factors
including Ets-1, CREB, and AP-2α but negatively regulated by SP-1/SP-3. In the present study, we have functionally
dissected the promoter of the mouse PP2A-Aβ gene. Our results demonstrate that three major cis-elements,
including the binding sites for Ets-1, SP1/SP3, and RXRα/β, are present in the proximal promoter of the mouse
PP2A-Aβ gene. Gel mobility shifting assays reveal that Ets-1, SP1/SP3, and RXRα/β all bind to PP2A-Aβ gene
promoter. In vitro mutagenesis and reporter gene activity assays demonstrate that while Ets-1 displays negative
regulation, SP1/SP3 and RXRα/β positively regulate the promoter of the PP2A-Aβ gene. Co-expression of the
cDNAs encoding Ets-1, SP1/SP3, or RXRα/β and the luciferase reporter gene driven by PP2A-Aβ promoter further
confirm their control over the PP2A-Aβ promoter. Finally, ChIP assays demonstrate that Ets-1, SP1/SP3, and
RXRα/β can all bind to the PP2A-Aβ gene promoter. Together, our results reveal that multiple transcription factors
regulate the PP2A-Aβ gene. Moreover, our results provide important information explaining why PP2A-Aα and
PP2A-Aβ display distinct expression levels.
