Article

Crystal structure of a minimal eIF4E-Cup complex reveals a general mechanism of eIF4E regulation in translational repression

Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany.
RNA (Impact Factor: 4.62). 07/2012; 18(9):1624-34. DOI: 10.1261/rna.033639.112
Source: PubMed

ABSTRACT Cup is an eIF4E-binding protein (4E-BP) that plays a central role in translational regulation of localized mRNAs during early Drosophila development. In particular, Cup is required for repressing translation of the maternally contributed oskar, nanos, and gurken mRNAs, all of which are essential for embryonic body axis determination. Here, we present the 2.8 Å resolution crystal structure of a minimal eIF4E-Cup assembly, consisting of the interacting regions of the two proteins. In the structure, two separate segments of Cup contact two orthogonal faces of eIF4E. The eIF4E-binding consensus motif of Cup (YXXXXLΦ) binds the convex side of eIF4E similarly to the consensus of other eIF4E-binding proteins, such as 4E-BPs and eIF4G. The second, noncanonical, eIF4E-binding site of Cup binds laterally and perpendicularly to the eIF4E β-sheet. Mutations of Cup at this binding site were shown to reduce binding to eIF4E and to promote the destabilization of the associated mRNA. Comparison with the binding mode of eIF4G to eIF4E suggests that Cup and eIF4G binding would be mutually exclusive at both binding sites. This shows how a common molecular surface of eIF4E might recognize different proteins acting at different times in the same pathway. The structure provides insight into the mechanism by which Cup disrupts eIF4E-eIF4G interaction and has broader implications for understanding the role of 4E-BPs in translational regulation.

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    • "FACT DNA Drosophila melanogaster [36] MeCP2 DNA Homo sapiens [27] [28] MBD2 NurD DNA Homo sapiens [94] Transcription factors Max DNA Homo sapiens [37] [95] NKX3.1 DNA Drosophila melanogaster [40] ApLLP DNA Aplysia kurodai [96] Neurogenin 1 DNA Homo sapiens [97] Ultrabithorax DNA, Exd Drosophila melanogaster [38] [44] HMGB1 DNA Rattus norvegicus [31] Oct-1 DNA Homo sapiens [39] Ets-1 DNA Mus musculus [29] [30] c-Myc Bin1 SH3 domain Homo sapiens [48] Nrf2 Keap1 Mus musculus [98] Prothymosin α Keap1 Homo sapiens [99] Coactivator interactions GCN4 Med15 Saccharomyces cerevisiae [46] [47] p65 (RelA) CBP TAZ1 Mus Musculus [100] p53 TAD CBP NCBD Homo sapiens [45] KID KIX Mus musculus [101] [102] Interactions with the basal machinery EWS PIC Homo sapiens [41] SP1 TFIID Homo sapiens [103] GCN4 PIC Saccharomyces cerevisiae [22] Gal4 PIC Saccharomyces cerevisiae [104] PC4 PIC Homo sapiens [105] Nuclear receptors, transport PPAR-γ DNA Homo sapiens [106] NLS Importin-α Xenopus laevis [16] [107] mRNA maturation, translation Cup eIF4E Drosophila melanogaster [108] UPF2 UPF1 Homo sapiens [13] RNAP II CTD mRNA maturation factors Saccharomyces cerevisiae [109] SF1 U2AF 65 Homo sapiens [110] 4E-BP2 eIF4E Homo sapiens [111] L7/L12 Ribosome Escherichia coli [112] [113] DNA repair RPA DNA Homo sapiens [32] [33] UmuD'2 UmuD2 Escherichia coli [114] UvrD DNA Escherichia coli [115] "
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    • "In combination with previous studies, our structures show that the canonical motifs of diverse 4E-BPs and eIF4G use a similar mechanism to bind eIF4E and that this binding mode is conserved (Gross et al., 2003; Kinkelin et al., 2012; Mizuno et al., 2008; Paku et al., 2012; Umenaga et al., 2011). In contrast, the binding mode of the linker regions and non-canonical motifs of 4E-BPs differ in the molecular details as expected on the basis of the differences in sequence and length of these regions. "
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    • "Interestingly, the D. melanogaster protein Cup, related to human 4E–T, has two nearby eIF4E-binding sites, the high-affinity one which conforms to the consensus, being Y342TRSRLM, with a second lower affinity and non-consensus one, ELEGRLR, some 30 residues downstream [34]. The second site binds laterally and perpendicularly in α-helix form to the eIF4E β-sheet [46], and plays a role in the stabilisation of associated mRNA [47]. "
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