Tudor domains are small protein structural motifs of about ~50 amino acids related to the “royal family” of methyl readers, which also includes chromo, MBT, PWWP, and Agenet-like domains. Tudor domains occur either alone, in tandem, or with other domains and are found in many proteins that are involved in RNA metabolism, germ cell development, transposon silencing, DNA damage response, histone modification, and chromatin remodeling. The tudor domains recognize symmetric methylated arginine or methylated lysine residues. Tudor domain proteins act as an oncogene and play a very important role in HCC and colon cancer. TDRD is also involved in RISC complex and interacts with AEG-1 oncogene. The tudor domain can bind to methylated arginine protein and promote tumor angiogenesis in human hepatocellular carcinoma, etc.