Identification of a conserved phosphorylation site modulating nuclear lamin polymerization.

Mitotic lamin disassembly results from phosphorylation at specific sites. In vitro, lamins can form head-to-tail polymers that disassemble upon phosphorylation by cdc2 kinase. A co-immunoprecipitation assay, employing Drosophila nuclear lamin Dm0 fragments was used to study the effect of phosphorylation on head-to-tail binding. Phosphorylation of serine-50 by cAMP-dependent kinase inhibited head-to-tail binding in the same manner as phosphorylation of serine-42 by cdc2 kinase. Results suggest that multiple pathways may be employed to disassemble nuclear lamins in vivo.