Characteristics of IRF4 and STAT3 mutations in ATL. (A) Box plots (median and interquartile values) of variant allele frequencies of recurrent mutations (n = 28) present in >3% of ATL cases. (B) Positions and types of STAT3 mutations detected by targeted capture sequencing for 414 ATL cases. The National Center for Biotechnology Information protein reference sequence for STAT3 is NP_003141.2. (C) Amino acid sequence alignment of Homo sapiens STAT3 with other STAT proteins using the ClustalW algorithm. The mutation and evolutionally conserved residues are shown in cyan and red, respectively. The phosphotyrosine binding sites and β-strands are also shown. (D) Frequently mutated amino acid residues mapped on the STAT3 protein. All recurrently mutated residues are present around the phosphotyrosine-binding pocket.