Rajaei, N.  Chiruvella, K. Lin, F. Åström, S.  Domesticated transposase Kat1 and its fossil imprints induce sexual differentiation in yeast. Proc. Natl Acad. Sci.  doi:10.1073/ pnas.1406027111


Transposable elements (TEs) are mobile genetic elements that colonize the nuclei of all organisms. Although TEs can be detrimental, they are considered important evolutionary forces. We discovered a domesticated TE in the mating-type locus of the yeast Kluyveromyces lactisK. lactis hobo/Activator/Tam3 (hAT) transposase 1 (Kat1) mobilizes this TE from the genome by inducing DNA double-strand breaks followed by gene conversion, resulting in a switch of mating type. Hence, Kat1 triggers an adaptive genome rearrangement facilitating sexual differentiation. Surprisingly, the translation of Kat1 requires a programmed frameshift. The frameshift in the KAT1 gene dampens the activity of Kat1. In contrast, Kat1 is transcriptionally activated by nutrient limitation. Together our results reveal Kat1 as a highly regulated transposase that stimulates sexual reproduction.