No abstract

The phosphorylation of eIF4E1 at serine 209 by MNK1 or MNK2 has been shown to initiate oncogenic mRNA translation, a process that favours cancer development and maintenance. Here, we interrogate the MNK-eIF4E axis in diffuse large B-cell lymphoma (DLBCL) and show a distinct distribution of MNK1 and MNK2 in germinal centre B-cell (GCB) and activated B-cell (ABC) DLBCL. Despite displaying a differential distribution in GCB and ABC, both MNKs functionally complement each other to sustain cell survival. MNK inhibition ablates eIF4E1 phosphorylation and concurrently enhances eIF4E3 expression. Loss of MNK protein itself downregulates total eIF4E1 protein level by reducing eIF4E1 mRNA polysomal loading without affecting total mRNA level or stability. Enhanced eIF4E3 expression marginally suppresses eIF4E1-driven translation but exhibits a unique translatome that unveils a novel role for eIF4E3 in translation initiation. We propose that MNKs can modulate oncogenic translation by regulating eIF4E1-eIF4E3 levels and activity in DLBCL.

The COVID-19 pandemic is a major threat to global health for which there are only 50 limited medical countermeasures, and we lack a thorough understanding of mechanisms of 51 humoral immunity 1,2 . From a panel of monoclonal antibodies (mAbs) targeting the spike 52 (S) glycoprotein isolated from the B cells of infected subjects, we identified several mAbs 53 that exhibited potent neutralizing activity with IC50 values as low as 0.9 or 15 ng/mL in 54 pseudovirus or wild-type (wt) SARS-CoV-2 neutralization tests, respectively. The most 55 potent mAbs fully block the receptor-binding domain of S (SRBD) from interacting with 56 human ACE2. Competition-binding, structural, and functional studies allowed clustering 57 of the mAbs into defined classes recognizing distinct epitopes within major antigenic sites 58 on the SRBD. Electron microscopy studies revealed that these mAbs recognize distinct 59 conformational states of trimeric S protein. Potent neutralizing mAbs recognizing unique 60 sites, COV2-2196 and COV2-2130, bound simultaneously to S and synergistically 61 neutralized authentic SARS-CoV-2 virus. In two murine models of SARS-CoV-2 infection, 62 passive transfer of either COV2-2916 or COV2-2130 alone or a combination of both mAbs 63 protected mice from severe weight loss and reduced viral burden and inflammation in the 64 lung. These results identify protective epitopes on the SRBD and provide a structure-based 65 framework for rational vaccine design and the selection of robust immunotherapeutic 66 cocktails. 67 68 The S protein of SARS-CoV-2 is the molecular determinant of viral attachment, fusion, and 69 entry into host cells 3 . The cryo-EM structure of a prefusion-stabilized trimeric S protein 70 ectodomain (S2Pecto) for SARS-CoV-2 reveals similar features to that of the SARS-CoV S 71 protein 4 . This type I integral membrane protein and class I fusion protein possesses an N-72

HIV-1 broadly neutralizing antibodies (bNAbs) are being explored as passively administered therapeutic and preventative agents. However, the extensively diversified HIV-1 envelope glycoproteins (Env) rapidly acquire mutations to evade individual bNAbs in monotherapy regimens. The use of a “single” agent to simultaneously target distinct Env epitopes is desirable to overcome viral diversity. Here, we report the use of tandem single-chain variable fragment (ScFv) domains of two bNAbs, specific for the CD4-binding site and V3 glycan patch, to form anti-HIV-1 bispecific ScFvs (Bi-ScFvs). The optimal Bi-ScFv crosslinks adjacent protomers within one HIV-1 Env spike and has greater neutralization breadth than its parental bNAbs. Furthermore, the combination of this Bi-ScFv with a third bNAb recognizing the Env membrane proximal external region (MPER) results in a trispecific bNAb, which has nearly pan-isolate neutralization breadth and high potency. Thus, multispecific antibodies combining functional moieties of bNAbs could achieve outstanding neutralization capacity with augmented avidity.

Deregulation of the translational machinery is emerging as a critical contributor to cancer development. The contribution of microRNAs in translational gene control has been established however; the role of microRNAs in disrupting the cap-dependent translation regulation complex has not been previously described. Here, we established that elevated miR-520c-3p represses global translation, cell proliferation and initiates premature senescence in HeLa and DLBCL cells. Moreover, we demonstrate that miR-520c-3p directly targets translation initiation factor, eIF4GII mRNA and negatively regulates eIF4GII protein synthesis. miR-520c-3p overexpression diminishes cells colony formation and reduces tumor growth in a human xenograft mouse model. Consequently, downregulation of eIF4GII by siRNA decreases translation, cell proliferation and ability to form colonies, as well as induces cellular senescence. In vitro and in vivo findings were further validated in patient samples; DLBCL primary cells demonstrated low miR-520c-3p levels with reciprocally up-regulated eIF4GII protein expression. Our results provide evidence that the tumor suppressor effect of miR-520c-3p is mediated through repression of translation while inducing senescence and that eIF4GII is a key effector of this anti-tumor activity.