Because tyrosine kinases mainly localize to the cytoplasm or the plasma membrane, most studies have focused on their roles in the cytoplasm. However, emerging evidence has revealed that tyrosine kinases also localize to the nucleus and regulate nuclear events, such as DNA damage responses, gene expression, and chromatin structural changes. In this paper, Takakura et al. showed that the truncated isoform of the receptor tyrosine kinase ALK (ALK ATI), which only has the intracellular kinase domain, regulates chromatin structural changes, heterochromatinization, and gene expression in the nucleus. This paper is the first report shedding light on the nuclear roles of ALK.