Polypeptide chain release factor eRF3 is a novel molecular partner of survivin

Development and therapeutic potential of GSPT1 molecular glue degraders: A medicinal chemistry perspective

Unprecedented therapeutic targeting of previously undruggable proteins has now been achieved by molecular-glue-mediated proximity-induced degradation. As a small GTPase, G1 to S phase transition 1 (GSPT1) interacts with eRF1, the translation termination factor, to facilitate the process of translation termination. Studied demonstrated that GSPT1 plays a vital role in the acute myeloid leukemia (AML) and MYC-driven lung cancer. Thus, molecular glue (MG) degraders targeting GSPT1 is a novel and promising approach for treating AML and MYC-driven cancers. In this Perspective, we briefly summarize the structural and functional aspects of GSPT1, highlighting the latest advances and challenges in MG degraders, as well as some representative patents. The structure-activity relationships, mechanism of action and pharmacokinetic features of MG degraders are emphasized to provide a comprehensive compendium on the rational design of GSPT1 MG degraders. We hope to provide an updated overview, and design guide for strategies targeting GSPT1 for the treatment of cancer.

West Nile Virus Subgenomic RNAs Modulate Gene Expression in a Neuronal Cell Line

Subgenomic flaviviral RNAs (sfRNAs) are small non-coding products of the incomplete degradation of viral genomic RNA. They accumulate during flaviviral infection and have been associated with many functional roles inside the host cell. Studies so far have demonstrated that sfRNA plays a crucial role in determining West Nile virus (WNV) pathogenicity. However, its modulatory role on neuronal homeostasis has not been studied in depth. In this study, we investigated the mechanism of sfRNA biosynthesis and its importance for WNV replication in neuronal cells. We found that sfRNA1 is functionally redundant for both replication and translation of WNV. However, the concurrent absence of sfRNA1 and sfRNA2 species is detrimental for the survival of the virus. Differential expression analysis on RNA-seq data from WT and ΔsfRNA replicon cell lines revealed transcriptional changes induced by sfRNA and identified a number of putative targets. Overall, it was shown that sfRNA contributes to the viral evasion by suppressing the interferon-mediated antiviral response. An additional differential expression analysis among replicon and control Neuro2A cells also clarified the transcriptional changes that support WNV replication in neuronal cells. Increased levels of translation and oxidative phosphorylation, post-translational modification processes, and activated DNA repair pathways were observed in replicon cell lines, while developmental processes such as axonal growth were deficient.

Degradation of GSPT1 causes TP53-independent cell death in leukemia while sparing normal hematopoietic stem cells

Targeted protein degradation is a rapidly advancing and expanding therapeutic approach. Drugs that degrade GSPT1 via the CRL4CRBN ubiquitin ligase are a new class of cancer therapy in active clinical development with evidence of activity against acute myeloid leukemia in early-phase trials. However, other than activation of the integrated stress response, the downstream effects of GSPT1 degradation leading to cell death are largely undefined, and no murine models are available to study these agents. We identified the domains of GSPT1 essential for cell survival and show that GSPT1 degradation leads to impaired translation termination, activation of the integrated stress response pathway, and TP53-independent cell death. CRISPR/Cas9 screens implicated decreased translation initiation as protective following GSPT1 degradation, suggesting that cells with higher levels of translation are more susceptible to the effects of GSPT1 degradation. We defined 2 Crbn amino acids that prevent Gspt1 degradation in mice, generated a knockin mouse with alteration of these residues, and demonstrated the efficacy of GSPT1-degrading drugs in vivo with relative sparing of numbers and function of long-term hematopoietic stem cells. Our results provide a mechanistic basis for the use of GSPT1 degraders for the treatment of cancer, including TP53-mutant acute myeloid leukemia.

Lithium Chloride Sensitivity in Yeast and Regulation of Translation

For decades, lithium chloride (LiCl) has been used as a treatment option for those living with bipolar disorder (BD). As a result, many studies have been conducted to examine its mode of action, toxicity, and downstream cellular responses. We know that LiCl is able to affect cell signaling and signaling transduction pathways through protein kinase C and glycogen synthase kinase-3, which are considered to be important in regulating gene expression at the translational level. However, additional downstream effects require further investigation, especially in translation pathway. In yeast, LiCl treatment affects the expression, and thus the activity, of PGM2, a phosphoglucomutase involved in sugar metabolism. Inhibition of PGM2 leads to the accumulation of intermediate metabolites of galactose metabolism causing cell toxicity. However, it is not fully understood how LiCl affects gene expression in this matter. In this study, we identified three genes, NAM7, PUS2, and RPL27B, which increase yeast LiCl sensitivity when deleted. We further demonstrate that NAM7, PUS2, and RPL27B influence translation and exert their activity through the 5′-Untranslated region (5′-UTR) of PGM2 mRNA in yeast.

Xp11.22 deletions encompassing CENPVL1, CENPVL2, MAGED1 and GSPT2 as a cause of syndromic X-linked intellectual disability

By searching a clinical database of over 60,000 individuals referred for array-based CNV analyses and online resources, we identified four males from three families with intellectual disability, developmental delay, hypotonia, joint hypermobility and relative macrocephaly who carried small, overlapping deletions of Xp11.22. The maximum region of overlap between their deletions spanned ~430 kb and included two pseudogenes, CENPVL1 and CENPVL2, whose functions are not known, and two protein coding genes-the G1 to S phase transition 2 gene (GSPT2) and the MAGE family member D1 gene (MAGED1). Deletions of this ~430 kb region have not been previously implicated in human disease. Duplications of GSPT2 have been documented in individuals with intellectual disability, but the phenotypic consequences of a loss of GSPT2 function have not been elucidated in humans or mouse models. Changes in MAGED1 have not been associated with intellectual disability in humans, but loss of MAGED1 function is associated with neurocognitive and neurobehavioral phenotypes in mice. In all cases, the Xp11.22 deletion was inherited from an unaffected mother. Studies performed on DNA from one of these mothers did not show evidence of skewed X-inactivation. These results suggest that deletions of an ~430 kb region on chromosome Xp11.22 that encompass CENPVL1, CENPVL2, GSPT2 and MAGED1 cause a distinct X-linked syndrome characterized by intellectual disability, developmental delay, hypotonia, joint hypermobility and relative macrocephaly. Loss of GSPT2 and/or MAGED1 function may contribute to the intellectual disability and developmental delay seen in males with these deletions.