The nuclear envelope breakdown in mitotic prophase involves depolymerization of lamin filaments, the main constituents of the nuclear lamina. The nuclear lamina is located at the nuclear face of the inner nuclear membrane and plays and important role in the structure and function of the nuclear envelope (reviewed by Burke and Stewart 2012). Depolymerization of lamin filaments, which consist of lamin homodimers associated through electrostatic interactions in head-to-tail molecular strings, is triggered by phosphorylation of lamins. While CDK1 phosphorylates the N-termini of lamins (Heald and McKeon 1990, Peter et al. 1990, Ward and Kirschner 1990, Mall et al. 2012), PKCs (PRKCA and PRKCB) phosphorylate the C-termini of lamins (Hocevar et al. 1993, Goss et al. 1994, Mall et al. 2012). PKCs are activated by lipid-mediated signaling, where lipins, activated by CTDNEP1:CNEP1R1 serine/threonine protein phosphatase complex, catalyze the formation of DAG (Gorjanacz et al. 2009, Golden et al. 2009, Wu et al. 2011, Han et al. 2012, Mall et al. 2012).
Nga Ly-Hartig, TB,