Figure 1. Schematic representation of PPP2R4 splice variants.

The top line represents the PPP2R4 gene. Exons are boxed (5 and 3 UTR are speckled). Introns and the 3 UTR are not drawn to scale. PTPA alpha and beta are the major transcripts/proteins; PTPA gamma, zeta and eta do not encode functional proteins and probably result from splicing errors.

Gene promoter has been analyzed and resides in a non-methylated CpG island. No TATA or CAAT box. Two functional yin-yang-1 (YY1) binding sites direct basal promoter expression. Tumor suppressor p53 represses transcription through a mechanism involving YY1 inhibition.

Figure 2. Schematic structure of the PPP2R4 promoter.

Two YY1 sites are required for basal PPP2R4 promoter activity and reside within the minimal promoter (nt -67/+38 relative to the start of transcription which is at +1). Upstream of this minimal promoter a GC-rich Sp1-cluster is present (nt -670/-470) of which the functionality has not yet been proven. The PPP2R4 promoter resides within an unmethylated CpG island.

Figure 3. PTPA protein structure.

PTPA is an all alpha-helical polypeptide, organized into two domains separated by a groove. Here the ribbon structure of human PTPA is displayed (derived from PDB code: 2IXM, Leulliot et al., 2006).