Disclosed herein are methods of modulation of the viability of a cell using fusion proteins comprising a transporter peptide sequence and a MYC polypeptide. Further disclosed herein are methods of modulating an immune response using the fusion proteins. Further disclosed herein are methods of identifying agents capable of modulation of the viability of a cell or an immune response. Further disclosed herein are agents and compositions capable of modulation of the viability of a cell or an immune response.