Gle1 Regulates RNA Binding of the DEAD-Box Helicase Ded1 in Its Complex Role in Translation Initiation

Abstract

DEAD-box proteins (DBPs) are required in gene expression to facilitate changes to ribonucleoprotein complexes, but the cellular mechanisms and regulation of DBPs are not fully defined. Gle1 is a multifunctional regulator of DBPs with roles in mRNA export and translation. In translation, Gle1 modulates Ded1, a DBP required for initiation. However, overexpression causes defects, suggesting that Ded1 can promote or repress translation in different contexts. Here we show that expression suppresses the repressive effects of , and Gle1 counteracts Ded1 in translation assays Furthermore, Ded1 and Gle1 both affect assembly of pre-initiation complexes. Through mutation analysis and binding assays, we show that Gle1 inhibits Ded1 by reducing its affinity for RNA. Our results are consistent with a model wherein active Ded1 promotes translation, but inactive or excess Ded1 leads to translation repression. Gle1 can inhibit either role of Ded1, positioning it as a gatekeeper to optimize Ded1 activity to the appropriate level for translation. This study suggests a paradigm for finely controlling the activity of DEAD-box proteins to optimize their function in RNA-based processes. It also positions the versatile regulator Gle1 as a potential node for the coordination of different steps of gene expression.

Depletion of mRNA export regulator DBP5/DDX19, GLE1 or IPPK that is a key enzyme for the production of IP6, resulting in differentially altered cytoplasmic mRNA expression and specific cell defect

“…cerevisiae [ 17 ]. Moreover, Gle1 regulates RNA binding of the DEAD-box helicase Ded1 in translation initiation[ 18 , 19 ]. Recently, it was also demonstrated that the localization of GLE1 in the centrosome plays a role in centrosome integrity [ 20 ].…”

Nup42 and IP6 coordinate Gle1 stimulation of Dbp5/DDX19B for mRNA export in yeast and human cells

“…In addition to regulating Dbp5 at the NPC, Gle1 is required for the function of distinct Dbps at non-NPC subcellular locales. In S. cerevisiae , Gle1-IP 6 regulates Dbp5 activity during translation termination, and Gle1 impacts the ATPase activity and RNA binding of Ded1, another DEAD-box protein, for efficient translation initiation independently of IP 6 12–15 . In humans, hGle1 shuttles between the nucleus and cytoplasm with at least two isoforms, hGle1A and hGle1B, produced from a single gene 11,16 .…”

Control of Translation at the Initiation Phase During Glucose Starvation in Yeast

“…Ded1p acts as an RNA-dependent helicase or ‘RNA chaperone’ and can remodel mRNP complexes. Ded1p can function as a translational repressor when present at high concentrations; its overproduction impairs yeast cell growth and induces the assembly of P-bodies or SGs [63,295]. To examine Ded1p localization in 15 min of glucose starvation, plasmids encoding Ded1p-GFP and Pub1p-mCherry were transformed into WT yeast and the fluorescence signals tested for co-localization against the non-starved cells.…”