Figure 1: Regulation of ABCG2 in undifferentiated or differentiated, hypoxia/reperfusion treated, physical or UV induced stress treated hESCs. (A) Undifferentiated hESCs express ABCG2 mRNA but lack ABCG2 protein. Whereas ABCG2 is down regulated by miR-519c and miR-520h, alternative mechanisms for loss of ABCG2 protein expression are alternative expression of 5’ and 3’ UTRs, repression of translation, and increased proteasome-mediated degradation. (B) Upon differentiation, hypoxia/reperfusion, physical or UV-induced stress, hESCs have altered regulation of ABCG2 allowing protein to be expressed. Mechanisms might include the use of alternative 5’ and 3’UTRs, decreased expression of miRNAs, increased translation, and decreased protein degradation.