The function of SDE2 (spliceosome associated SDE2, ENSG00000143751) is as follows. Inhibits translesion DNA synthesis by preventing monoubiquitination of PCNA, this is necessary to counteract damage due to ultraviolet light-induced replication stress (PubMed:27906959). SDE2 is cleaved following PCNA binding, and its complete degradation is necessary to allow S-phase progression following DNA damage (PubMed:27906959). . Plays a role in pre-mRNA splicing by facilitating excision of relatively short introns featuring weak 3'-splice sites (ss) and high GC content (PubMed:34365507). May recruit CACTIN to the spliceosome (By similarity). {ECO:0000250|UniProtKB:O14113, ECO:0000269|PubMed:34365507}. Plays a role in ribosome biogenesis by enabling SNORD3- and SNORD118-dependent cleavage of the 47S rRNA precursor (PubMed:34365507). Binds ncRNA (non-coding RNA) including the snoRNAs SNORD3 and SNORD118 (PubMed:34365507). .