Repair of HCMV-induced DNA Damage in infected Cells
Human Cytomegalovirus (HCMV) is the major viral cause of birth defects, infecting 1-2% of all newbornsannually. Approximately 5-10% of these congenitally infected infants will manifest signs of seriousneurological damage at birth, which can include deafness, blindness, mental retardation and microcephaly.Another 10-15% will develop sensori-neural hearing loss and/or learning disabilities within the first 10 yearsof life. Our long-term goat is to understand the mechanism behind the development of morbidity andmortality in infants congenitally infected with HCMV. Over the last several years we have studied theinteraction of HCMV with the cell cycle and DNA repair machinery of the permissively infected cell. We havediscerned that HCMV sequesters many key regulatory and repair proteins into its viral replication centers.However, it appears to partition the components of several complexes so that all the proteins are presentwithin the replication centers, but not all are available to the cellular genome. We have also determined thatHCMV can induce specific damage on chromosome 1 during S-phase. When coupled with the literature regarding nonspecific damage induced at late times post infection ourdata more clearly highlights the genotoxic effects of HCMV. We hypothesize that long-term detrimentalconsequences to the cellular genome may occur if 1) the initial specific damage is propagated or 2) damageincurred at late times post infection is not repaired due to sequestration of the repair machinery. To test ourhypothesis, we propose three specific aims. First, we will thoroughly define the parameters of chromosomelq breakage in HCMV-infected cells with regard to rapidity of induction and cell cycle phase at time ofinfection. We think it is imperative that our results be moved into more clinically relevant cell types, especiallycells of neural lineage, as these are the cells most severely affected by the virus during congenital infection.Second, we also will determine the consequences of chromosome 1 damage in these clinically relevantcells, and whether in a semi-permissive environment we can observe propagation of the chromosome 1damage instead of healing of the break or movement of the cell toward apoptosis. Lastly, we willcharacterize the ability of HCMV-infected cells to repair exogenously introduced damage at late times postinfection, after viral replication centers are assembled.