RECQL4 and Rothmund-Thomson syndrome: Interestingly, the human RECQL4 helicase defective in the chromosomal instability and premature aging disorder Rothmund-Thomson syndrome was found in a complex with the ubiquitin ligases UBR1 and UBR2 that are implicated in protein proteolysis; however, RECQL4 protein was determined to lack ubiquitylation and be relatively stable in unstressed HeLa cells, suggesting some other role for its interaction, perhaps subcellular localization [64].