Required for pre-mRNA splicing as component of the spliceosome. Contributes to pre-mRNA splicing after spliceosome formation and prior to the first transesterification reaction. ATP + H2O = ADP + H(+) + phosphate Component of pre-catalytic spliceosome complexes. Belongs to the DEAD box helicase family. DEAH subfamily. DDX16/PRP8 sub-subfamily.