JUN and Ewing sarcoma: In previous work, using a RRM1 knockout-rescue model and gene-expression analysis, we identified that DNA replication stress upregulates the expression of multiple AP-1 transcription factors in Ewing sarcoma cells and that expression of the canonical AP-1 transcription factors c-Jun and c-Fos is sufficient to downregulate the level of the c-Myc oncoprotein and inhibit cell growth [15].