Functions as a scaffold that mediates the ordered assembly of spliceosomal proteins and snRNAs. Required for the assembly of the U4/U6-U5 tri-snRNP complex (By similarity). Required for embryo development (Ref.3). Required for splicing efficiency of COOLAIR introns and usage of the proximal poly(A) site. COOLAIR is a set of long non-coding antisense transcripts produced at the FLOWERING LOCUS C (FLC). COOLAIR initiates just downstream of the major sense transcript poly(A) site and terminates either early or extends into the FLC promoter region. Splicing of COOLAIR by PRP8A is functionally important for FLC regulation (PubMed:24725596). Interacts with CLO. Embryonic lethality due to abnormal suspensor development.