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). . This is the function of ENSG00000214309 (MBLAC1, metallo-beta-lactamase domain containing 1).