E2F1 activates MFN2 expression by binding to the promoter and decreases mitochondrial fission and mitophagy in HeLa cells.

Mitofusin-2 (MFN2) is primarily involved in mitochondrial fusion and participates in diverse biological processes. Several reports show that MFN2 is a target of different miRNAs; however, the transcriptional regulation of MFN2 has not been extensively studied. To gain insight into the transcriptional regulation of MFN2, we expressed E2F transcription factor 1 (E2F1) exogenously and observed that it increased the endogenous expression of MFN2 by binding to its putative promoter region. Although the levels of E2F1 were shown to vary during the cell cycle, the expression of MFN2 and its regulator SP1 did not change throughout the different phases, suggesting that E2F1 regulates MFN2 in a cell-cycle-independent manner. In the cell-cycle phases, where the expression of E2F1 was reduced, SP1 might act in its place to regulate the expression of MFN2. We showed that E2F1 and SP1 are present as a complex on the promoter of MFN2 during the S-phase as well as in E2F1 overexpressing cells, suggesting that they may regulate the expression of MFN2 synergistically. Furthermore, we found that E2F1 modulated mitochondrial fusion and mitophagy, likely through regulation of MFN2. Bioinformatic analysis revealed that several potential targets of E2F1 are localized in mitochondria and associated with autophagy. Collectively, these data identify the E2F1-MFN2 axis as a regulator of mitochondrial morphology and mitophagy, suggesting a potential therapeutic target for the treatment of mitochondrial disorders.