Rkhd3, also known as MEX3B is a member of a novel family of four homologous human MEX3 proteins each containing two heterogeneous nuclear ribonucleoprotein K homology (KH) domains and one carboxy-terminal RING finger module. MEX3 proteins, including Rkhd3, are phosphoproteins that bind RNA through their KH domains and shuttle between the nucleus and the cytoplasm via the CRM1 export pathway. These proteins are a novel family of evolutionarily conserved RNA-binding proteins, differentially recruited to P bodies and potentially involved in post-transcriptional regulatory mechanisms. Rkhd3 is thought to act as a mechanism to fine-tune mRNA regulation in early Xenopus development, and with Rkhd4, but not Rkhd1, will co-localize with both the hDcp1a decapping factor and Argonaute (Ago) proteins in processing bodies (P bodies), recently characterized as centers of mRNA turnover.Synonyms: KIAA2009, RING finger and KH domain-containing protein 3, RING finger protein 195, RNA-binding protein MEX3B, RNF195