Figure 7.

Proposed mechanism for retrograde signaling that links mitochondrial transcript processing to cell proliferation. The impairment of primary transcript processing in mitochondria decreases abundance of mRNAs, encoding protein subunits of the respiratory chain. Inactivation of complexes I and V increases mitochondrial ROS formation. Accumulating ROS lead to oxidative stress with cellular and DNA damage. To withstand low-level oxidative stress, cells initiate a specific transcriptional response, which enforces the G2 checkpoint via the cycB-Cdk1 inhibitors Gadd45 and Tob, and promotes cell survival by lowering intracellular ROS levels and allowing DNA repair before mitosis.