Cell lines from the heredrtary darters Cockayne Syrrtome (CS) and Warner Syndrome (WS) exhtxtphenofypes of prematnaging and serve as model systems tar aging stud". CS (Group B), WS, and other agKelated dsordars (Bloom, Xerodama Pigmentosum (Groups B and D)) are characterized by mutations in related genes exhbting conserved motifs of sequence homotogy. The molecular defects responsible for the clinical phenotypes of these dseases remain to be determined, but presumMty relate to (he functional activities of these conserved proteins in chromosome metabolism. CSB protein, by sequence comparison, belongs to the SNF2 family of proteins which have roles in Iranscriptional regulation, chromosome stability and DMA repar. The role of CSB protein in trarscriptkm-coupled repair is currently under investigation. The complex clinical phenotype of CS suggests that DNA repair may not be the primary leconsrstentwlhevTder" AfrcrilhislabcretoryltalCSceilsexrlailelicwmlrariscrpt)0(i A functional analysis of the CSB gene has been undertaken to better understand the nature of the molecular deficiencies observed in CS. Site-specific mutants are being tested for genetic complementation of the C S strain CS1AN by cell viability, RNA synthesis recovery and gene-specific repair upon exposure to UV light. In addition, genébc complementation studws have been used to address Ire molecular genetic role of CSB protein in RNA pol ll-medeled transcription using an In vfvo assay. The premature aging syndrome WS is characterized by homozygous recessive mutations in the WRN gene which shares significant sequence homology to the CSB gene. A hallmark molecular defect of WSisgenomicinstabity. Hypermutable Kgation of DNA ends may lead to instability durirn the process" of replication, repair, or recombination. To address this mechanism, the rate and fidelity of ligation of DNA plasmids with 5′ protruding ends or single stranded and double stranded breaks induced by ionizing radntion was assessed In vfvo using WS and normal cells. These data will be dscussed in relation to the molecular basis of genomic instability in WS. Moreover, the establishment of a functional assay for WS deficiency in vitro nil be used for structure-function studies of the WRN protein.
|Published - 1997