KH domain-containing, RNA-binding, signal transduction-associated protein 1 is a protein that in humans is encoded by the KHDRBS1 gene. This gene encodes a member of the K homology domain-containing, RNA-binding, signal transduction-associated protein family. The encoded protein appears to have many functions and may be involved in a variety of cellular processes, including alternative splicing, cell cycle regulation, RNA 3'-end formation, tumorigenesis, and regulation of human immunodeficiency virus gene expression. Sam68 (the Src-Associated substrate in Mitosis of 68 kDa) is officially called KHDRBS1 (KH domain containing, RNA binding, signal transduction associated 1). Sam68 is a KH-type RNA binding protein that recognizes U (U/A)AA direct repeats with relative high affinity. Sam68 is predominantly nuclear and its major function in the nucleus is to regulate alternative splicing by recognizing RNA sequences neighboring the included/excluded exon (s).