As HIF is a transcription factor, we next analysed the levels of KDM2A and KDM2B mRNAs in the presence or absence of HIF subunits (Figure 4). Both KDM2A and KDM2B mRNA levels in HeLa and U2OS cells were dependent on the presence of HIF-1α and HIF-1β in hypoxia (Figure 4A,B, Figure S4A). These results suggest that KDM2 family is transcriptionally regulated by HIF-1, which results in changes in protein levels in hypoxia. Similarly, overexpression of HIF-1α could induce KDM2A mRNA levels in both cells lines in normoxia and hypoxia (Figure 4C, Figure S4B). Interestingly, HIF-1α overexpression also resulted in increased levels of KDM2B, but this was only observed under normoxic conditions (Figure 4C, Figure S4B).