Formation of @entity376 63-linked poly-ubiquitin chains protects @entity1 lung cells against XXXX -induced mutagenicity.

@entity1 @entity1364 @entity137 @entity16 @entity3014 @entity59327 @entity13285 @entity376 @entity12847 @entity4624 @entity375 @entity105
@entity3014 exerts its mutagenic effects via induction of @entity4624 ( @entity12847 )-DNA adducts. Such helix-distorting adducts are not always successfully repaired prior to DNA replication, which may result in a blocked replication fork. To alleviate this stall, cells utilize DNA damage tolerance systems involving either @entity16 avoidance or error-prone translesion synthesis. Studies in @entity375 suggest the modification of @entity1364 by @entity376 63-linked poly-ubiquitin (K63-polyUb) chains as a key mediator of the @entity16 avoidance pathway. Recently, we extended this observation to @entity1 cells, showing the occurrence of poly-ubiquitination of @entity1364 in UV-irradiated @entity1 cells. In the present study, we hypothesized that disrupting the formation of K63-polyUb chains inhibits damage avoidance and favors error-prone repair involving low-fidelity polymerases (e.g. POLeta), causing increased @entity12847 -induced mutagenicity. To test this hypothesis, we generated A549 cells expressing either a mutant ubiquitin ( @entity59327 -Ub) which blocks further ubiquitination through K63, or the wild type ubiquitin (WT-Ub). We show that @entity1364 is poly-ubiquitinated in these cells upon @entity12847 -exposure and that disruption of K63-polyUb chain formation has no effect on @entity12847 -induced @entity137 . In contrast, significantly higher frequencies of @entity12847 -induced HPRT mutations were observed in @entity59327 -Ub expressing cells, of which the majority (74%) was @entity13285 transversion. @entity12847 treatment caused an enhanced recruitment of POLeta to the replication machinery of the @entity59327 -Ub expressing cells, where it co-localized with @entity1364 . Suppression of POLeta expression by using siRNA resulted in a 50% reduction of @entity12847 -induced mutations in the @entity59327 cells. In conclusion, we demonstrated that formation of K63-polyUb chains protects @entity12847 -exposed @entity1 cells against translesion synthesis-mediated mutagenesis. These findings indicate that K63-polyubiquitination guards against @entity105 by preventing mutagenesis and thus contributing to genomic stability.
