Component of the MAC complex that probably regulates defense responses through transcriptional control and thereby is essential for plant innate immunity. Possesses a sequence specific DNA sequence 'CTCAGCG' binding activity. Involved in mRNA splicing and cell cycle control. May also play a role in the response to DNA damage. Component of the multiprotein assembly MOS4-associated complex (MAC) at least composed of MOS4, CDC5, PRL1 and PRP19. Interacts with PRL1, MOS4 and PRP19A. Associated with the spliceosome. Expressed extensively in shoot and root meristems. Accelerated cell death. Enhanced susceptibility to virulent and avirulent pathogens. Belongs to the CEF1 family.