Changes in mRNA stability play an important role in the adaptation of yeast cells to iron deprivation.

ABSTRACT

Eukaryotic cells rely on iron as an indispensable cofactor for multiple biological functions including mitochondrial respiration and protein synthesis. The budding yeast Saccharomyces cerevisiae utilizes both transcriptional and posttranscriptional mechanisms to couple mRNA levels to the requirements of iron deprivation. Thus, in response to iron deficiency, transcription factors Aft1 and Aft2 activate the expression of genes implicated in iron acquisition and mobilization, whereas two mRNA-binding proteins, Cth1 and Cth2, posttranscriptionally control iron metabolism. By using a genome-wide approach, we describe here a global stabilization of mRNAs, including transcripts encoding ribosomal proteins (RPs), when iron bioavailability diminishes. mRNA decay assays indicate that the mRNA-binding protein Pub1 contributes to RP transcript stabilization during adaptation to iron limitation. In fact, Pub1 becomes critical for growth and translational repression in low-iron conditions. Remarkably, we observe that pub1Δ cells also exhibit an increase in the transcription of RP genes that evidences the crosstalk between transcription and degradation mechanisms to maintain the appropriate mRNA balance under iron deficiency conditions.