TIP41, TOR Signaling Pathway Regulator Like Protein (TIPRL)

TIPRL is an inhibitory regulator of protein phosphatase-2A (PP2A), PP4 , and PP6. TIP isoform-2 did not interact with PP2A, suggesting that the C terminus of TIP is important for PP2A binding. Incubation of PP2A with TIP, but not TIP isoform-2, resulted in dose-dependent inhibition of PP2A phosphatase activity. Cells in which TIP was depleted by small interfering RNA exhibited decreased phosphorylation of a 32-kD substrate of ATM/ATR kinases.

TIP is an inhibitory regulator of PP2A and that the TIP/PP2A complex has a role within the ATM/ATR signaling pathway controlling DNA replication and repair.The predicted protein contains 272 amino acids. Immunoblot analysis showed ubiquitous expression of a 33-kD TIP protein.