By SDS-PAGE of human 20S U5 snRNP, followed by EST database analysis, and PCR of a HeLa cell cDNA library, Reuter et al. (1999) cloned TXNL4A, which they called U5-15KD. The deduced protein contained 142 amino acids and contains a thioredoxin-like domain. TXNL4A shares 66% sequence identity with the S. cerevisiae homolog Dib1.

Jin et al. (2006) expressed tagged DIM1 in E. coli and performed enzyme cleavage assays on the purified proteins. They found that DIM1 has peptidase activity and undergoes autocleavage. Protease inhibitors EDTA, chymostatin, and 6-aminohexanoic acid inhibited DIM1 cleavage, and the cleaved dominant-negative form of DIM1 retained the autocleavage activity of the full-length protein.