Component of the nuclear pore complex (NPC); a complex required for the trafficking across the nuclear envelope. Functions as a scaffolding element in the nuclear phase of the NPC essential for normal nucleocytoplasmic transport of proteins and mRNAs; plays a role in the establishment of nuclear-peripheral chromatin compartmentalization in interphase; and in the mitotic spindle checkpoint signaling during mitosis. Involved in the quality control and retention of unspliced mRNAs in the nucleus. Implicated in nuclear export of mRNAs transcribed from heat shock gene promoters. May play a limited role in the regulation of nuclear protein export. May be involved in the formation and/or maintenance of NPC-associated perinuclear heterochromatin exclusion zones (HEZs). Finally; may act as a spatial regulator of the spindle-assembly checkpoint (SAC) response (By similarity). {ECO:0000250}.