Multisite phosphorylation of nuclear interaction partner of ALK (NIPA) at G2/M involves cyclin B1/Cdk1.
Nuclear interaction partner of ALK (NIPA) is an F-box-containing protein that defines a nuclear skp1 cullin F-box (SCF)-type ubiquitin E3 ligase (SCFNIPA) implicated in the regulation of mitotic entry. The SCFNIPA complex targets nuclear cyclin B1 for ubiquitination in interphase, whereas phosphorylation of NIPA in late G2 phase and mitosis inactivates the complex to allow for accumulation of cyclin B1. Here, we identify the region of NIPA that mediates binding to its substrate cyclin B1. In addition to the recently described serine residue 354, we specify 2 new residues, Ser-359 and Ser-395, implicated in the phosphorylation process at G2/M within this region. Moreover, we found cyclin B1/Cdk1 to phosphorylate NIPA at Ser-395 in mitosis. Mutation of both Ser-359 and Ser-395 impaired effective inactivation of the SCFNIPA complex, resulting in reduced levels of mitotic cyclin B1. These data are compatible with a process of sequential NIPA phosphorylation where cyclin B1/Cdk1 amplifies phosphorylation of NIPA once an initial phosphorylation event has dissociated the SCFNIPA complex. Thus, cyclin B1/Cdk1 may contribute to the regulation of its own abundance in early mitosis.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.