SMYD3,also name as ZMYND1 and ZNFN3A1,belongs to the histone-lysine methyltransferase family.It is a histone methyltransferase that plays an important role in transcriptional regulation in human carcinogenesis. It can specifically methylate histone H3 at lysine 4 and activate the transcription of a set of downstream genes,including several oncogenes (e.g.,N-myc,CrkL,Wnt10b,RIZ and hTERT) and genes involved in the control of cell cycle.. It plays an important role in transcriptional activation as a member of an RNA polymerase complex. SMYD3 is frequently overexpressed in different types of cancer cells. It functions as a coactivator of Era and potentiates Era activity in response to ligand. SMYD3 as a new coactivator for ER-mediated transcription,providing a possible link between SMYD3 overexpression and breast cancer. The common variable number of tandem repeats polymorphism in SMYD3 is a susceptibility factor for some types of human cancer. .