Bex3 associates with replicating mitochondria and is involved in possible growth control of F9 teratocarcinoma cells

Bex3 expression and possible function in growth control were studied. It was expressed in a limited number of organs, including gonads and hippocampal regions of the brain. Visualized by deconvolution microscopy as a GFP-fusion protein in F9 teratocarcinoma cells, Bex3 localized, along with concentrations of actin, at perinuclear mitochondria that were undergoing active DNA replication. Bex3 association with mitochondria required a nuclear export signal (NES) and the C-terminal four amino acids (CaaX box), and siRNA reduction of Bex3 levels led to slow or negligible growth rates of the F9 cells. Thus, Bex3 may be required in target tissues for mitochondrial function at a distinct phase of the cellular growth cycle.