Characterizing a novel contact site between mitochondria and the nucleus

Mitochondrial functions are crucial for cellular homeostasis. The biogenesis, quality control and activity of mitochondria are tightly regulated by the nucleus, thus, extensive communication between the two organelles must exist. One way by which two organelles can communicate is through membrane contact sites, areas of close apposition held together by tethering proteins. Although many such contact points have been discovered and characterized, a mitochondria-nucleus contact site was not previously described in yeast. Using fluorescent and electron microscopy in Saccharomyces Cerevisiae, we demonstrate areas of contact between the two organelles in vivo. Excitingly, we show that these contact sites are not facilitated by the Endoplasmic reticulum (ER)-mitochondria encounter structure (ERMES) complex that creates the contact between ER and nucleus, pointing towards a unique function. A high throughput screen revealed several resident proteins most with unknown function. We show that over-expression of some of these proteins increases the extent of the contact, placing them as potential tethers. Elucidating the different mechanisms that allow mitochondrial crosstalk with the nucleus will allow better understanding of mitochondrial functions in health and disease.