The presence of the nuclear envelope in eukaryotes functionally separates the processes of transcription and translation. The ability to have these processes disjoined serves to establish greater transcriptional and translational regulation. The nuclear envelope consists of an outer nuclear membrane, which is contiguous with the endoplasmic reticulum, and an inner nuclear membrane (INM). The INM contains numerous integral membrane proteins that bind to both lamins and chromatin-associated proteins. One of these proteins, emerin, directly binds the nuclear lamina and a chromatin associated protein named Barrier-to-Autointegration (BAF). Interestingly, mutation or deletion of emerin causes the recessive form of Emery-Dreifuss muscular dystrophy (EDMD). Although emerin is expressed in most cell types tested, EDMD specifically targets muscle and adipose tissue, suggesting a role for emerin in tissue-specific functions. Recently it has been demonstrated that another INM protein, Lap213, interacts with a transcriptional repressor, germ-cell-less (GCL). Since Lab2beta and emerin share a significant region of homology, I tested whether emerin could interact with transcriptional repressors. Both GCL and EBP1, another transcriptional regulator, bind emerin. I propose that emerin may recruit transcriptional regulators to the nuclear envelope and form functional repressor or activator complexes here. To test this model, I will fine-map the functional domains within emerin, GCL, and EBP1 necessary for this interaction. Using mutational analysis, I will identify the domain(s) in emerin that interact(s) with GCL and EBP1. Mutations will also be made in GCL and EBP in order to map the 'emerin binding domain' in each of these proteins. Once identified, the(se) emerin binding domain(s) will be used to identify other emerin binding proteins. The initial characterization of these interactions will serve as the foundation for studying the role of the nuclear envelope in transcriptional regulation in my own laboratory.
