FIGURE 7.

Mutations in the UBA domain of SCCRO are present in human cancers. A, frameshift mutation in the UBA domain identified in one case of 47 lung and head and neck squamous cell carcinomas assessed by use of the Sequenom method. A truncated SCCRO mutant without a UBA domain is predicted. B, mutations in SCCRO identified in TCGA projects. Red dots represent UBA domain point mutations or splice mutations putatively producing truncated SCCRO without a UBA domain; light blue dots represent non-UBA domain mutations. Each dot represents a separate cancer. The asterisk (*) indicates a nonsense mutation. C, immunoprecipitation (IP) assay using MYC-SCCRO and its TCGA UBA mutants on Lys⁴⁸- or Lys⁶³-linked ubiquitin chains followed by Western blot analysis for ubiquitin showing that TCGA-identified UBA domain mutants do not bind ubiquitin chains. D, immunoblot (IB) analysis of lysates from U2OS cells transfected with MYC-SCCRO or TCGA UBA mutants probed with antibody against ubiquitinated proteins following immunoprecipitation for MYC showing that all mutants lose the ability to bind to polyubiquitinated proteins. EV, empty vector.