How can a single protein be involved in this many seemingly unrelated biological functions? This stems from the fact that Tat is an intrinsically disordered protein with no welldefined secondary structures . As a result of this structural plasticity that allows it to adopt many conformations in solution, Tat can interact with a large repertoire of proteins and receptors in infected and non-infected cells . Amongst them, a prominent one is p53 which is known as a cellular tumor suppressor . In a cell, p53 is a homotetrameric transcription factor that positively and negatively regulates the expression of diverse genes, whereby it governs diverse downstream events, including glycolysis , autophagy , the regulation of oxidative stress , angiogenesis and so forth. Furthermore, this regulatory protein serves a function in the cellular response to numerous cellular stresses and ultimately coordinates the cell cycle and apoptosis. Taken together, p53 is decisive in the survival and death of abnormal cells .