Human PPP1R26P1 functions as cis-repressive element in mouse Rb1.
The human retinoblastoma gene (RB1) is imprinted; the mouse Rb1 gene is not.Imprinted expression of RB1 is due to differential methylation of a CpG island (CpG85), which is located in the pseudogene PPP1R26P1 in intron 2 of RB1.CpG85 serves as promoter for an alternative RB1 transcript, which is expressed from the unmethylated paternal allele only