Endoribonuclease that catalyzes the hydrolysis of histone-coding pre-mRNA 3′-end. Involved in histone pre-mRNA processing during the S-phase of the cell cycle, which is required for entering/progressing through S-phase (PubMed:30507380). Cleaves histone pre-mRNA at a major and a minor cleavage site after the 5′-ACCCA-3′ and the 5′-ACCCACA-3′ sequence, respectively, and located downstream of the stem-loop (PubMed:30507380). May require the presence of the HDE element located at the histone pre-RNA 3′-end to avoid non-specific cleavage (PubMed:30507380).
