Chapter 5. Nuclear Membrane Protein Emerin: Roles in Gene Regulation, Actin Dynamics and Human Disease

Summary

Loss of emerin, a nuclear membrane protein, causes Emery-Dreifuss muscular dystrophy (EDMD), characterized by muscle weakening, contractures of major tendons and potentially lethal cardiac conduction system defects. Emerin has a LEM-domain and therefore binds barrier-to-autointegration factor (BAF), a conserved chromatin protein essential for cell division. BAF recruits emerin to chromatin and regulates higher-order chromatin structure during nuclear assembly. Emerin also binds filaments formed by Atype lamins, mutations in which also cause EDMD. Other partners for emerin include nesprin-1a and transcriptional regulators such as germ cell-less (GCL). The binding affinities of these partners range from 4 nM (nesprin-1α) to 200nM (BAF), and are physiologically significant. Biochemical studies therefore provide a valid means to predict the properties of emerin–lamin complexes in vivo. Emerin and lamin A together form stable complexes with either BAF or GCL in vitro. BAF, however, competes with GCL for binding to emerin in vitro. These and additional partners, notably actin and nuclear myosin I, suggest disease-relevant roles for emerin in gene regulation and the mechanical integrity of the nucleus.