The function of PRPF31 (pre-mRNA processing factor 31, ENSG00000105618) is as follows. Involved in pre-mRNA splicing as component of the spliceosome (PubMed:11867543, PubMed:20118938, PubMed:28781166). Required for the assembly of the U4/U5/U6 tri-snRNP complex, one of the building blocks of the spliceosome (PubMed:11867543). {ECO:0000269|PubMed:11867543, ECO:0000269|PubMed:20118938, ECO:0000269|PubMed:28781166}.