Getting lamin B1 processed and organized

Lamins are the building blocks of the nuclear lamina, a complex polymer attached to the nuclear envelope that is thought to be important for nuclear stability, chromatin organization, and gene expression. On page 1223, Maske et al. identify the protease responsible for processing lamin B1, demonstrate the existence of a nuclear receptor specific for carboxymethylated lamin B1, and show that posttranslational processing may control the localization of this lamin into subdomains within the nuclear envelope.

After being farnesylated, the COOH-terminal CAAX domain of lamin B1 is cleaved by an endoprotease, and the new COOH terminus of the protein is then methylated by the enzyme Icmt. Using a monoclonal antibody that distinguishes proteolyzed from unproteolyzed lamin B1, the authors determined that proteolysis specifically requires the CAAX endoprotease Rce1. Separate pools of farnesylated but unproteolyzed and proteolyzed but unmethylated...