Component of a protein complex required for cotranscriptional processing of 3'-ends of polyadenylated and histone pre-mRNA. Interacts with Cpsf73 and Cpsf100 forming a core cleavage factor required for both polyadenylated and histone mRNA processing. Interacts with Slbp and Lsm11. Concentrates in the histone locus body. The HEAT repeats have been determined based on 3D-structure analysis and are not detected by sequence-based prediction programs. Belongs to the Symplekin family.