Previous studies on Flag-tagged Cyclin D1 in mice have shown that this protein can regulate gene expression by interacting with transcription factors and epigenetic modifiers in cancer cells and mouse embryos (Fu et al. 2005a,b; Landis et al. 2006; Geng et al. 2007; Sicinski et al. 2007; Bienvenu et al. 2010; Casimiro et al. 2012). Here, CCND1 is linked to cancer.