Conservation of polyamine regulation by translational frameshifting from yeast to mammals.
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Recombinant S. pombe SPA (spa1) protein directly inhibits S. pombe ornithine decarboxylase in vitro, establishing ODC inhibitor activity for this gene.
"the recombinant protein can inhibit S.pombe ODC"
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Deletion of spa1 raises intracellular putrescine, spermidine and cadaverine, while overexpression depletes all polyamines, showing spa1 negatively regulates polyamine biosynthesis.
"The cellular concentrations of putrescine, spermidine and cadaverine (but not spermine) were higher in the knockout strains than in wild-type cells."
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spa1 is the primary negative regulator of ODC activity in S. pombe in both growing and non-dividing cells.
"This suggests that SPA is the primary regulator of ODC activity in S.pombe, not only during cell growth (short term regulation) but also in non-dividing cells (longer term regulation)."
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Full-length spa1 requires a polyamine-responsive +1 ribosomal frameshift for expression, forming an autoregulatory feedback circuit.
"a significant reduction (6.5-fold) in frameshifting efficiency in SPA-overproducing cells that correlates with a decrease of polyamine content"
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Complete deletion of spa1 does not affect viability, growth, mating or morphology under standard conditions.
"Complete deletion of SPA (both ORFs) did not affect the viability of S.pombe cells in rich (YE) or minimal (MM) media."