| Structural highlights
Function
[IF4E_MOUSE] Recognizes and binds the 7-methylguanosine-containing mRNA cap during an early step in the initiation of protein synthesis and facilitates ribosome binding by inducing the unwinding of the mRNAs secondary structures. May play an important role in spermatogenesis through translational regulation of stage-specific mRNAs during germ cell development (By similarity). Its translation stimulation activity is repressed by binding to the complex CYFIP1-FMR1. Component of the CYFIP1-EIF4E-FMR1 complex which binds to the mRNA cap and mediates translational repression. In the CYFIP1-EIF4E-FMR1 complex this subunit mediates the binding to the mRNA cap.[1]
Publication Abstract from PubMed
The 5' cap consists of 7-methylguanosine (m(7)G) linked by a 5'-5'-triphosphate bridge to messenger RNA (mRNA) and acts as the master regulator of mRNA turnover and translation initiation in eukaryotes. Cap analogues that influence mRNA translation and turnover (either as small molecules or as part of an RNA transcript) are valuable tools for studying gene expression, which is often also of therapeutic relevance. Here, we synthesized a series of 15 dinucleotide cap (m(7)GpppG) analogues containing a 5'-phosphorothiolate (5'-PSL) moiety (i.e., an O-to-S substitution within the 5'-phosphoester) and studied their biological properties in the context of three major cap-binding proteins: translation initiation factor 4E (eIF4E) and two decapping enzymes, DcpS and Dcp2. While the 5'-PSL moiety was neutral or slightly stabilizing for cap interactions with eIF4E, it significantly influenced susceptibility to decapping. Replacing the gamma-phosphoester with the 5'-PSL moiety (gamma-PSL) prevented beta-gamma-pyrophosphate bond cleavage by DcpS and conferred strong inhibitory properties. Combining the gamma-PSL moiety with alpha-PSL and beta-phosphorothioate (PS) moiety afforded first cap-derived hDcpS inhibitor with low nanomolar potency. Susceptibility to Dcp2 and translational properties were studied after incorporation of the new analogues into mRNA transcripts by RNA polymerase. Transcripts containing the gamma-PSL moiety were resistant to cleavage by Dcp2. Surprisingly, superior translational properties were observed for mRNAs containing the alpha-PSL moiety, which were Dcp2-susceptible. The overall protein expression measured in HeLa cells for this mRNA was comparable to mRNA capped with the translation augmenting beta-PS analogue reported previously. Overall, our study highlights 5'-PSL as a synthetically accessible cap modification, which, depending on the substitution site, can either reduce susceptibility to decapping or confer superior translational properties on the mRNA. The 5'-PSL-analogues may find application as reagents for the preparation of efficiently expressed mRNA or for investigation of the role of decapping enzymes in mRNA processing or neuromuscular disorders associated with decapping.
5'-Phosphorothiolate Dinucleotide Cap Analogues: Reagents for Messenger RNA Modification and Potent Small-Molecular Inhibitors of Decapping Enzymes.,Wojtczak BA, Sikorski PJ, Fac-Dabrowska K, Nowicka A, Warminski M, Kubacka D, Nowak E, Nowotny M, Kowalska J, Jemielity J J Am Chem Soc. 2018 May 1. doi: 10.1021/jacs.8b02597. PMID:29676910[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Napoli I, Mercaldo V, Boyl PP, Eleuteri B, Zalfa F, De Rubeis S, Di Marino D, Mohr E, Massimi M, Falconi M, Witke W, Costa-Mattioli M, Sonenberg N, Achsel T, Bagni C. The fragile X syndrome protein represses activity-dependent translation through CYFIP1, a new 4E-BP. Cell. 2008 Sep 19;134(6):1042-54. doi: 10.1016/j.cell.2008.07.031. PMID:18805096 doi:http://dx.doi.org/10.1016/j.cell.2008.07.031
- ↑ Wojtczak BA, Sikorski PJ, Fac-Dabrowska K, Nowicka A, Warminski M, Kubacka D, Nowak E, Nowotny M, Kowalska J, Jemielity J. 5'-Phosphorothiolate Dinucleotide Cap Analogues: Reagents for Messenger RNA Modification and Potent Small-Molecular Inhibitors of Decapping Enzymes. J Am Chem Soc. 2018 May 1. doi: 10.1021/jacs.8b02597. PMID:29676910 doi:http://dx.doi.org/10.1021/jacs.8b02597
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