Fbxw5 suppresses nuclear c-Myb activity via DDB1-Cul4-Rbx1 ligase-mediated sumoylation.

The c-myb proto-oncogene product (c-Myb) is degraded in response to Wnt-1 signaling. In this process, Fbxw7α, the F-box protein of the SCF complex, binds to c-Myb via its C-terminal WD40 domain, and induces the ubiquitination of c-Myb. Here, we report that Fbxw5, another F-box protein, enhances sumoylation of nuclear c-Myb.

Ribosomal protein L4 positively regulates activity of a c-myb proto-oncogene product.

The c-myb proto-oncogene product (c-Myb) induces transcription of a group of target genes involved in the G1/S transition and in anti-apoptosis. The level of c-Myb is negatively regulated by the Wnt signal, but it remains obscure how c-Myb activity is positively regulated. We have found that ribosomal protein L4 (RPL4) binds to the DNA-binding domain of c-Myb.