Werner syndrome: genetic and molecular basis of a premature aging disorder.

Werner syndrome (WS) is a rare autosomal recessive disorder characterized by genomic instability and by the premature onset of a number of age-related diseases, including cancers. The gene responsible for WS encodes a protein that has an exonuclease domain and a domain similar to DNA helicases of the RecQ-like subfamily. Accumulating evidence indicates that the WS gene product is involved in resolving aberrant DNA structures that may arise during the process of DNA replication and transcription. Such processes generate regions of single-stranded DNA that may inadvertently provide a substrate for the initiation of recombination. Various mechanisms have evolved to ensure that recombination does not occur promiscuously during these events, and results are consistent with a model in which the WS protein is part of one such mechanism.