The DEAD-box helicase Ded1 from yeast is an mRNP cap-associated protein that shuttles between the cytoplasm and nucleus.
Bottom Line: In addition, we show that Ded1 is genetically linked to these factors.Ded1 comigrates with these proteins on sucrose gradients, but treatment with rapamycin does not appreciably alter the distribution of Ded1; thus, most of the Ded1 is in stable mRNP complexes.We conclude that Ded1 is an mRNP cofactor of the cap complex that may function to remodel the different mRNPs and thereby regulate the expression of the mRNAs.
Affiliation: Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France Université Paris-Sud, Ecole Doctorale 426 GGC, Orsay, France.Show MeSH
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Mentions: We reasoned that, since Ded1 was present in the nucleus, it might interact with the nuclear cap-binding complex. To test for this, we used a slow-growth variant of Ded1 that was mutated in the Q motif involved in adenine binding of ATP [Ded1-F162C; (71)]. We then overexpressed various candidate proteins to see if they could partially restore the growth phenotype (Figure 2A). The overexpressed Cbp20 and eIF4G2 proteins restored the growth to nearly wildtype levels. Cbp80 partially restored growth, while Pab1 and eIF4G1 promoted growth at 18°C but inhibited growth at the higher temperatures. This latter result pointed to a synthetic lethal (inhibitory) effect of the overexpressed proteins. Indeed, we saw growth inhibition at all temperatures when we overexpressed Pab1 and eIF4G1 in a strain expressing the wildtype Ded1, which indicated that the inhibitory effects were unrelated to Ded1 (Figure 2B). Thus, all five of the tested proteins interacted genetically with Ded1.
Affiliation: Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France Université Paris-Sud, Ecole Doctorale 426 GGC, Orsay, France.