Human ribosomal protein L9 is a Bax suppressor that promotes cell survival in yeast

Abstract

The identification of a human ribosomal protein L9 (hRPL9) cDNA as a sequence capable of suppressing the lethal effects of heterologously expressed murine Bax in yeast led us to investigate its antiapoptotic potential. Using growth and viability assays, we show that yeast cells heterologously expressing hRPL9 are resistant to the growth inhibitory and lethal effects of exogenously supplied copper, indicating that it has pro-survival properties. To explore potential mechanisms, we used yeast mutants defective in all three types of programmed cell death (apoptosis, necrosis, and autophagy). The ability to retain pro-survival function in all the mutants suggests that hRPL9 may regulate a common pro-death process. In contrast, the yeast RPL9 orthologues, RPL9A and RPL9B, have opposite effects when overexpressed in yeast. In effect, instead of showing resistance to stress, RPL9A and RPL9B overexpressing cells show reduced cell growth. Further analysis indicates that the effects of overexpressed RPL9A and RPL9B are not in themselves lethal, instead, they serve to increase cell doubling time. Thus, yeast RPL9s are more representative of RPs whose extra-ribosomal function is similar to that of tumor suppressors. Taken together, our results demonstrate that RPL9 represents a species- and sequence-specific regulator of cell growth and survival.

Human Thyroid Cancer-1 (TC-1) is a vertebrate specific oncogenic protein that protects against copper and pro-apoptotic genes in yeast

“…In order to determine whether TC-1 could protect against other stressors besides Bax, cell-death-inducing levels of copper sulfate were used 59. Using the spot assay with increasing concentrations of copper sulfate, the cells harbouring only the vector show reduced growth, while cells harbouring TC-1 and 14-3-3 expressing plasmids remain largely unaffected (Figure 2A).…”

“…Sub-lethal level of a mild stress is often required to activate over-expressed native pro-apoptotic proteins for them to induce cell death. Here we used copper sulfate at a concentration that is known to be sub-lethal 59. Cultures of yeast doubly transformed with different combinations of expression vectors, including empty vectors, pro-apoptotic genes and TC-1 or 14-3-3 were serially diluted and spotted on nutrient agar media containing galactose alone or with sub-lethal copper sulfate (Figure 3A).…”

“…The YCA1 ∆ and YBH3 ∆ deletion strains were isogenic to BY4742 59. The plasmids expressing the cDNAs for human 14-3-3β/α and TC-1 (Bh1) as well as yeast YBH3 , YCA1 , AIF1 and YBH3 expressed under the control of the GAL1 -galactose-inducible promoter, were previously isolated and described 282930315253.…”

“…Viability assays were repeated for a minimum of three times and a minimum one hundred colonies were counted for each assay. Alternatively the cells were stained with the vital dye for 10 minutes then viability was determined by microscopical examination of at least 300 cells in three different experiments 59. In order to activate the proteins that are overexpressed from the different pro-apoptotic genes, the cells were treated with sub-lethal levels of copper (1.6 mM for agar plates and 1.0 mM for liquid cultures).…”

Topological centrality-based identification of hub genes and pathways associated with acute viral respiratory infection in infants

“…It was shown that RPL3 over-expression caused an increase in its aberrantly spliced mRNA, which was degraded by the nonsense-mediated decay pathway (Malygin et al, 2007). Moreover, RPL3 might play an important role in silencing the human embryonic epsilon-globin gene expression (Huang et al, 2000), and its over-expression led to growth inhibition (Eid et al, 2013). Strong down-regulation of the steady state mRNA level of RPL3 was observed upon induction of differentiation in HL-60 cells (Mailhammer et al, 1992).…”