Factor interacting with PAPOLA and CPSF1 (i.e, FIP1L1; also termed Pre-mRNA 3'-end-processing factor FIP1) is a protein that in humans is encoded by the FIP1L1gene (also known as Rhe, FIP1, and hFip1).[5][6] A medically important aspect of the FIP1L1 gene is its fusion with other genes to form fusion genes which cause clonal hypereosinophilia and leukemic diseases in humans.