Human RNA lariat debranching enzyme protein 1 – A surveillant for branch RNAs for degradation

Splicing is a processs to remove introns from precursor of mRNAs (pre-mRNAs). Introns are excised as a lariat form, and they should be debranched before degradation. This reaction is conferred by a RNA lariat debranching enzyme 1 (Dbr1) protein. The Dbr1 protein is evolutionarily conserved among many species and shares GNHE motif for debranching activity that is identical to protein phosphatase activity center. The human Dbr1 protein has a bipartite type nuclear localization signal, and it shuttles between the nucleus and the cytoplasm, suggesting novel function(s) in the cytoplasm. The human Dbr1 protein interacts with two proteins, Xab2 and hDrn1. Since Xab2 is involved in not only splicing but also transcription-coupled DNA repair (TCR), hDbr1 may also have a role in TCR. Although the function of hDrn1 is not known yet, this protein specifically interact with carboxy terminal of hDbr1 and it is also a nucleo-cytoplasmic shuttling protein. A heterodimer of hDbr1-hDrn1 may have role(s) in both in the nucleus and the cytoplasm of human cells.