RNF40 and breast cancer: Further supporting this phenomenon of a breast cancer subtype-specific function of RNF40 and H2Bub1, Wegwitz and colleagues have shown that the RNF40-H2Bub1 axis actually supports growth of HER2-positive (HER2+) breast cancers, both in vitro and in vivo, via transcriptional activation of genes involved in maintenance of the actin cytoskeleton.