The PP2A-Aβ gene is regulated by multiple transcriptional factors including Ets-1, SP1/SP3, and RXRα/β
2012
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.
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