RAN is a small GTPase involved in the assembly of microtubules to form mitotic spindles. The protein encoded by this gene is a cytoplasmic guanine nucleotide exchange factor (GEF) that binds beta-tubulin and has GEF activity toward RAN. The encoded protein plays a role in the formation of noncentrosomal microtubules. In addition, this protein may be involved in the regulation of D(1) receptor signaling by protein kinase C delta and protein kinase C gamma. Several transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Feb 2016].