Identification of novel genetic factors that control chronological lifespan in Schizosaccharomyces pombe during long term nitrogen starvation in a competitive environment

In this study we identified novel genetic players of chronological lifespan (CLS) by studying survival of quiescent fission yeast in a nitrogen depleted environment where cells are in a non-dividing state. A pool of the prototroph deletion library was maintained in media without nitrogen for 19 weeks and mutants that survived the longest in those conditions were identified by barcode sequencing. Mutants impaired in autophagy and entry/maintenance into quiescence activities are not detected to survive, as expected, throughout the time course of nitrogen starvation. Several genes identified here were also shown in the literature to exhibit similar pro-aging activity such as the translation initiation factor TIF213, APL1-APL3-APS2 subunits of the AP-2 adaptor complex which is involved in protein sorting at the plasma membrane, SPO4 serine/threonine kinase and SET9 methyltransferase. Novel long lived mutants identified and their extended lifespan when compared to the wild type was verified individually in isogenic cultures; those are mutants lacking Hht1 histone, Abp2 ARS binding protein, Cmk2 MAPK activated protein kinase, Mrc1 mediator of replication checkpoint, Vps66 predicted acyltransferase, Ncs1 calcium sensor, Tfs1 transcription factor, Plb1 phospholipase. Growth profiling of the mutants in deletion library pool was also performed in this study but a correlation between lifespan and growth was not detected. Finally, extended lifespan when compared to wild type was confirmed for thirty out of the thirty one mutants tested which shows excellent efficiency of this screen to identify mutants associated with chronological lifespan.