"SHOP ONCE, ENJOY TWICE" BY DUAL TARGETING: SINGLE GENES AND SINGLE PROTEINS, YET, IN TWO COMPARTMENTS WITH TWO FUNCTIONS

Dual targeting has emerged as an important aspect of gene expression in eukaryotes; single genes that give rise to proteins (termed echoproteins) that are localized to two (or more) subcellular locations. To address this topic, we have used Saccharomyces cerevisiae as a model eukaryotic organism and employed bioinformatics together with an independent screen of more than 300 yeast genes. Our results indicate that 1) strikingly, a third of the mitochondrial proteome is dual targeted, and suggested that this abundant dual targeting presents an evolutionary advantage, 2) dual localized mitochondrial proteins constitute a subgroup of mitochondrial proteins with distinctive properties such as MTS (mitochondrial targeting sequence) strength and protein net charge and 3) dual targeted proteins are more evolutionarily conserved supporting the notion that evolution of dual targeting is driven by function.

In this talk I will discuss experimental approaches that allow the detection of dual localized proteins and identification of their dual functions in each sub-cellular compartment. These include an alpha-complementation based dual localization screen/assay and approaches to specifically deplete an individual echoprotein from a specific compartment. I will briefly refer to the dual targeting and dual function of four mitochondrial proteins in yeast; aconitase (TCA cycle/Glyoxylate shunt), fumarase (TCA cycle/DNA damage response), Nfs1 (Iron cluster assembly/essential nuclear function) and Hsp60 (Chaperone/modulator of the proteasome).