Disclosed are sulfonamidoquinoline compounds, as well as pharmaceutical compositions and methods of use. One embodiment is a compound having the structure and pharmaceutically acceptable salts, prodrugs and N-oxides thereof (and solvates and hydrates thereof), wherein R1, R2, R3 and R4 are as described herein. In certain embodiments, a compound disclosed herein inhibits ubiquitination, and can be used to treat disease by blocking the degradation of tumor suppressors.