LZAP is a novel Wip1 binding partner and positive regulator of its phosphatase activity in vitro

ABSTRACT

The phosphatase Wip1 attenuates the DNA damage response (DDR) by removing phosphorylation marks from a number of DDR proteins (p53, MDM2, Chk1/2, p38). Wip1 also dephosphorylates and inactivates RelA. Notably, LZAP, a putative tumor suppressor, has been linked to dephosphorylation of several of these substrates, including RelA, p38, Chk1, and Chk2. LZAP has no known catalytic activity or functional motifs, suggesting that it exerts its effects through interaction with other proteins. Here we show that LZAP binds Wip1 and stimulates its phosphatase activity. LZAP had been previously shown to bind many Wip1 substrates (RelA, p38, Chk1/2), and our results show that LZAP also binds the previously identified Wip1 substrate, MDM2. This work identifies 2 novel Wip1 substrates, ERK1 and HuR, and demonstrates that HuR is a binding partner of LZAP. Pleasingly, LZAP potentiated Wip1 catalytic activity toward each substrate tested, regardless of whether full-length substrates or phosphopeptides were utilized. Since this effect was observed on ERK1, which does not bind LZAP, as well as for each of 7 peptides tested, we hypothesize that LZAP binding to the substrate is not required for this effect and that LZAP directly binds Wip1 to augment its phosphatase activity.

KEYWORDS:

• CDK5RAP3
• C53
• LZAP
• phosphatase regulator
• PPM1D
• PP25; Wip1

This article is referred to by:

LZAP: A break on phosphorylation

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Funding

This work was supported by the National Institute of Dental and Craniofacial Research under R01 DE013173.

Author contributions

Conceived the experiments: JJW NI HA XL LD WGY. Provided reagents: LD. Conducted the experiments: JJW NI. Analyzed the data: JJW NI WGY. Prepared the figures: JJW. Wrote the manuscript: JJW NI WGY. All authors reviewed the manuscript.