Identification of nuclear βII protein kinase C as a mitotic lamin kinase

Valerie L. Goss, Barbara A. Hocevar, Larry J. Thompson, Carl A. Stratton, David J. Burns, Alan P. Fields

Research output: Contribution to journalArticlepeer-review

169 Scopus citations

Abstract

Multisite phosphorylation of the nuclear lamins is thought to regulate the process of mitotic nuclear envelope breakdown in vivo. Here we investigate the involvement of two proposed human mitotic lamin kinases, βII protein kinase C (PKC) and p34cdc2/cyclin B kinase, in human lamin B1 phosphorylation in vitro and in intact cells. We find that both kinases can phosphorylate purified soluble lamin B at similar rates. However, βII PKC phosphorylates interphase nuclear envelope lamin B at more than 200 times the rate of human p34cdc2/cyclin B kinase. βII PKC-mediated phosphorylation of lamin B is confined to two sites, Ser395 and Ser405, within the carboxyl-terminal domain, whereas human p34cdc2/cyclin B kinase phosphorylates a single site, Ser23, in the aminoterminal domain. A second potential p34cdc2/cyclin B kinase site within the carboxyl-terminal domain, Ser393, is not phosphorylated by human p34cdc2/cyclin B kinase. However, invertebrate p34cdc2/cyclin B kinase from sea star exhibits a different specificity, phosphorylating both amino- and carboxyl-terminal sites. Mitotic human lamin B from intact cells is phosphorylated predominantly in its carboxyl-terminal domain. Comparative tryptic phosphopeptide mapping demonstrates that the βII PKC site, Ser405, is a prominent target of mitotic lamin B phosphorylation in vivo. βIIPKC translocates to the nucleus during the G2/M phase of cell cycle concomitant with phosphorylation of Ser405, indicating a physiologic role for nuclear βII PKC activation in mitotic lamin B phosphorylation ira vivo. The presence of phosphorylation sites within the carboxyl-terminal domain of mitotic lamin B which are not phosphorylated by either βII PKC or p34cdc2/cyclin B kinase suggests the involvement of other lamin kinase(s) in G2/M phase lamin B phosphorylation.

Original languageEnglish (US)
Pages (from-to)19074-19080
Number of pages7
JournalJournal of Biological Chemistry
Volume269
Issue number29
StatePublished - Jul 22 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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