KHDRBS1, also known as Sam68 and p62, is an RNA-binding protein containing a KH domain. It has a calculated molecular mass of 48.2 kDa but migrates as a 68 kDa protein on SDS-PAGE. KHDRBS1 is phosphorylated by ERK and binds to the exonic splice-regulatory elements of an alternatively spliced exon, namely, exon v5 of CD44. This exon is frequently included in the course of tumor progression and upon the T cell activation. The inhibition of KHDRBS1 phosphorylation decreases the inclusion of the v5 exon sequence in mRNA. Therefore, KHDRBS1 plays a crucial role in alternative splicing of CD44 exon v5 induced by the RAS pathway. KHDRBS1 is localized at the nucleus or membrane but accumulates in the cytoplasm when its methylation is inhibited by PRMT1. Therefore, it can be concluded that methylation is required for the appropriate localization of KHDRBS1.