For 10 points, name this double-layered structure that surrounds the nucleus.
In flies, the recruitment of MSL proteins to sites within this structure is necessary for dosage compensation, and KASH domain proteins interact with SUN domain proteins within this structure.  Nesprins anchor this structure to the actin cytoskeleton, while emerin and other proteins containing LEM domains help anchor it to a proteinaceous structure on its inner surface.  In most organisms this structure is destroyed during cell division and is subsequently reformed from the endoplasmic reticulum under the guidance of the lamin A receptor.  125-megadalton protein complexes composed of Nups form channels through this structure, allowing mRNAs and proteins containing NES sequences to be exported to the cytoplasm.  For 10 points, name this double-layered structure that surrounds the nucleus.
In flies, the recruitment of MSL proteins to sites within this structure is necessary for dosage compensation, and KASH domain proteins interact with SUN domain proteins within this structure.  
nuclear envelope (accept nuclear membrane, perinuclear envelope, nucleolemma, or karyotheca; nuclear lamina and nucleus are not acceptable at any point)