The WD40 protein WDR5 is a core subunit of the human MLL and SET1 (hCOMPASS) histone H3 Lys4 (H3K4) methyltransferase complexes[1]. WDR5 consists of 334 amino acids and contains seven typical WD40 repeat domains, each approximately 40 amino acids, adopting a seven-bladed beta-propeller fold. It has been proposed that WDR5 is the component of the MLL complex that interacts directly with dimethylated H3K4 and is required for transition to trimethylation by the MLL complex. More recently, however, It has been demonstrated that yeast CPS30 and its mammalian homolog, WDR5, are required for complex assembly and that no H3K4 methylation is observed in their absence, indicating that WDR5 is central for complex assembly and activity. WDR5 plays important roles in developmental events, transcriptional regulation, and leukemogenesis[2]. Interestingly, it has been revealed that WDR5 was not only localized in the nucleus, but also abundantly localized in the cytoplasm, and hypothesized to play a role in  viral infections[3].