Purinosomes represent biomolecular condensates that compartmentalize all six enzymes in the de novo purine synthesis (DNPS) pathway to enhance the pathway flux. Previously, we found that purinosome-inducing cues, such as purine depletion and electron transport chain inhibition, promote the ubiquitination of DNPS enzyme PAICS through upregulating ASB11, a substrate adaptor of Cul5 E3 ligase. The ubiquitinated PAICS recruits UBPA2, a Ub-binding protein with multiple intrinsically disordered regions, to confer multivalent interactions for triggering phase separation in vitro and purinosome assembly in vivo. Importantly, purinosomes are constitutively formed in melanoma due to the high ASB11 expression, and purinosome formation supplies sufficient purine for melanoma proliferation and survival. Recently, we found that chemotherapeutic agents induce purinosome formation through a distinct mechanism that also involves ubiquitination. The detailed purinosome assembly mechanism in this circumstance, the differential role of Ub-binding proteins in controlling phase separation, and the potential impact of purinosome targeting on cancer therapy will be discussed.