Dissecting mRNA decay and translation inhibition during iron deficiency

Iron participates as a vital cofactor in multiple metabolic pathways. Despite its abundance, iron bioavailability is highly restricted in aerobic and alkaline environments. Therefore, living organisms have evolved multiple adaptive mechanisms to respond to iron scarcity. These strategies include a global remodeling of iron metabolism directed to optimize iron utilization. In the baker's yeast Saccharomyces cerevisiae, this metabolic reorganization is accomplished to a large extent by an mRNA-binding protein called Cth2. Yeast Cth2 belongs to a conserved family of tandem zinc finger containing proteins that specifically bind to transcripts with AU-rich elements and promote their turnover. A recent study has revealed that Cth2 also inhibits the translation of its target mRNAs (Ramos-Alonso et al., PLoS Genet 14:e1007476, https://doi.org/10.1371/journal.pgen.1007476 , 2018). Interestingly, the mammalian Cth2 ortholog known as tristetraprolin (aka TTP/TIS11/ZFP36), which is also implicated in controlling iron metabolism, promotes the decay and prevents the translation of its regulated transcripts. These observations open the possibility to study the relative contribution of altering mRNA stability and translation to the physiological adaptation to iron deficiency, the function played by the different domains within the mRNA-binding protein, and the potential factors implicated in coordinating both post-transcriptional events.