Introduction: Current prognostic markers have improved survival prediction, however, it has not
advanced treatment strategies. Gene expression profiling may identify biological markers suitable as
therapeutic targets. Leukaemia stem cell is associated with adverse outcome, however, its biological
characteristics are still being investigated. We observed higher in vitro cell viability in acute myeloid
leukaemia (AML) samples with poor prognosis, which may be stem cell related. Objective: The
objective of this study was to profile highly expressed genes in an AML sample of poor prognosis/high
viability and compare with a sample of good prognosis/low viability. Method: Subtractive hybridization
was performed on two AML samples with high blast counts (>80%), a poor prognosis, PP (disease free
survival, DFS12 months) sample. The PP sample had
higher CD34+ counts (73% vs 46%) and higher cell viability than the GP sample. cDNA libraries were
subsequently cloned and sequenced. Results: cDNA subtracted from the PP samples was identified
as genes active during fetal/embryonic development (LCOR, CNOT1, ORMDL1), HOX- related genes
(HOXA3, PBX3, SF3B1), hematopoiesis (SELL, IL-3RA) and aerobic glycolysis/hypoxia (PGK1,
HIGD1A) -associated genes. Majority of GP clones isolated contained genes involved in oxidative
phosphorylation, OXPHOS (COXs, ATPs, MTND4 and MTRNR2), protein synthesis (including
ribosomal proteins, initiating and elongation factors), chromatin remodeling (H2AFZ, PTMA), cell
motility (MALAT1, CALM2, TMSB4X), and mitochondria (HSPA9, MPO) genes. Conclusion: Thus,
the PP sample exhibited stem cell-like features while the GP sample showed cells at a high level of cell
activity. These genes are potential prognostic markers and targets for therapy.
Reactive oxygen species (ROS) are toxic by-products of normal aerobic metabolism. ROS can damage mRNAs and the translational apparatus resulting in translational defects and aberrant protein production. Three mRNA quality control systems monitor mRNAs for translational errors: nonsense-mediated decay, non-stop decay (NSD) and no-go decay (NGD) pathways. Here, we show that factors required for the recognition of NSD substrates and components of the SKI complex are required for oxidant tolerance. We found an overlapping requirement for Ski7, which bridges the interaction between the SKI complex and the exosome, and NGD components (Dom34/Hbs1) which have been shown to function in both NSD and NGD. We show that ski7 dom34 and ski7 hbs1 mutants are sensitive to hydrogen peroxide stress and accumulate an NSD substrate. We further show that NSD substrates are generated during ROS exposure as a result of aggregation of the Sup35 translation termination factor, which increases stop codon read-through allowing ribosomes to translate into the 3΄-end of mRNAs. Overexpression of Sup35 decreases stop codon read-through and rescues oxidant tolerance consistent with this model. Our data reveal an unanticipated requirement for the NSD pathway during oxidative stress conditions which prevents the production of aberrant proteins from NSD mRNAs.