multistep skin carcinogenesis assays were performed with mice with keratinocyte - specific deletion of the cnb1 gene ( cnb1xk5-crepr1)3 in parallel with cre - negative controls ( cnb1 ) . detailed conditions for these assays as well as chromatin immunoprecipitation , immunoblotting , immunofluorescence , senescence -galactosidase staining , biotinylated dna pull down assays , and sorting can be found in the method section and supplementary figure legends .