PUMILIO competes with AUF1 to control DICER1 RNA levels and miRNA processing

Environmental arsenic pollution induced liver oxidative stress injury by regulating miR-155 through inhibition of AUF1

Arsenic (As), a common environmental pollutant, has become a hot topic in recent years due to its potentially harmful effects. Liver damage being a central clinical feature of chronic arsenic poisoning. However, the underlying mechanisms remain unclear. We demonstrated that arsenic can lead to oxidative stress in the liver and result in structural and functional liver damage, significantly correlated with the expression of AUF1, Dicer1, and miR-155 in the liver. Interestingly, knockdown AUF1 promoted the up-regulatory effects of arsenic on Dicer1 and miR-155 and the inhibitory effects on SOD1, which exacerbated oxidative damage in rat liver. However, overexpression of AUF1 reversed the up-regulatory effects of arsenic on Dicer1 and miR-155, restored arsenic-induced SOD1 depletion, and attenuated liver oxidative stress injury. Further, we verified the mechanism and targets of miR-155 in regulating SOD1 by knockdown/overexpression of miR-155 and nonsense mutant SOD1 3'UTR experiments. In conclusion, these results powerfully demonstrate that arsenic inhibits AUF1 protein expression, which in turn reduces the inhibitory effect on Dicer1 expression, which promotes miR-155 to act on the SOD1 3'UTR region after high expression, thus inhibiting SOD1 protein expression and enzyme activity, and inducing liver injury. This finding provides a new perspective for the mechanism research and targeted prevention of arsenic poisoning, as well as scientific evidence for formulating strategies to prevent and control environmental arsenic pollution.

Eubacterium coprostanoligenes alleviates chemotherapy-induced intestinal mucositis by enhancing intestinal mucus barrier

Chemotherapy-induced mucositis represents a severe adverse outcome of cancer treatment, significantly curtailing the efficacy of these treatments and, in some cases, resulting in fatal consequences. Despite identifying intestinal epithelial cell damage as a key factor in chemotherapy-induced mucositis, the paucity of effective treatments for such damage is evident. In our study, we discovered that Eubacterium coprostanoligenes promotes mucin secretion by goblet cells, thereby fortifying the integrity of the intestinal mucus barrier. This enhanced barrier function serves to resist microbial invasion and subsequently reduces the inflammatory response. Importantly, this effect remains unobtrusive to the anti-tumor efficacy of chemotherapy drugs. Mechanistically, E. copr up-regulates the expression of AUF1, leading to the stabilization of Muc2 mRNA and an increase in mucin synthesis in goblet cells. An especially significant finding is that E. copr activates the AhR pathway, thereby promoting the expression of AUF1. In summary, our results strongly indicate that E. copr enhances the intestinal mucus barrier, effectively alleviating chemotherapy-induced intestinal mucositis by activating the AhR/AUF1 pathway, consequently enhancing Muc2 mRNA stability.

The in vivo functional significance of PUF hub partnerships in C. elegans germline stem cells

PUF RNA-binding proteins are conserved stem cell regulators. Four PUF proteins govern self-renewal of Caenorhabditis elegans germline stem cells together with two intrinsically disordered proteins, LST-1 and SYGL-1. Based on yeast two-hybrid results, we previously proposed a composite self-renewal hub in the stem cell regulatory network, with eight PUF partnerships and extensive redundancy. Here, we investigate LST-1-PUF and SYGL-1-PUF partnerships and their molecular activities in their natural context - nematode stem cells. We confirm LST-1-PUF partnerships and their specificity to self-renewal PUFs by co-immunoprecipitation and show that an LST-1(AmBm) mutant defective for PUF-interacting motifs does not complex with PUFs in nematodes. LST-1(AmBm) is used to explore the in vivo functional significance of the LST-1-PUF partnership. Tethered LST-1 requires this partnership to repress expression of a reporter RNA, and LST-1 requires the partnership to co-immunoprecipitate with NTL-1/Not1 of the CCR4-NOT complex. We suggest that the partnership provides multiple molecular interactions that work together to form an effector complex on PUF target RNAs in vivo. Comparison of LST-1-PUF and Nanos-Pumilio reveals fundamental molecular differences, making LST-1-PUF a distinct paradigm for PUF partnerships.

Functional significance of PUF partnerships in C. elegans germline stem cells

PUF RNA-binding proteins are conserved stem cell regulators. Four PUF proteins govern self-renewal of C. elegans germline stem cells together with two intrinsically disordered proteins, LST-1 and SYGL-1. Based on yeast two-hybrid results, we proposed a composite self-renewal hub in the stem cell regulatory network, with eight PUF partnerships and extensive redundancy. Here, we investigate LST-1-PUF and SYGL-1-PUF partnerships and their molecular activities in their natural context - nematode stem cells. We confirm LST-1-PUF partnerships and their specificity to self-renewal PUFs by co-immunoprecipitation and show that an LST-1(A m B m ) mutant defective for PUF-interacting motifs does not complex with PUFs in nematodes. LST-1(A m B m ) is used to explore the functional significance of the LST-1-PUF partnership. Tethered LST-1 requires the partnership to repress expression of a reporter RNA, and LST-1 requires the partnership to co-immunoprecipitate with NTL-1/Not1 of the CCR4-NOT complex. We suggest that the partnership provides multiple molecular interactions that work together to form an effector complex on PUF target RNAs. Comparison of PUF-LST-1 and Pumilio-Nanos reveals fundamental molecular differences, making PUF-LST-1 a distinct paradigm for PUF partnerships.

Summary statement

Partnerships between PUF RNA-binding proteins and intrinsically disordered proteins are essential for stem cell maintenance and RNA repression.

The Potential of NORAD-PUMILIO-RALGAPB Regulatory Axis as a Biomarker in Breast Cancer

Introduction: Long non-coding RNAs (LncRNA) represent a heterogeneous family of RNAs that have emerged as regulators of various biological processes through their association with proteins in ribonucleoproteins complexes. The dynamic of these interactions can affect cell metabolism, including cancer development. Annually, breast cancer causes thousands of deaths worldwide, and searching for new biomarkers is pivotal for better diagnosis and treatment. Methods: Based on in silico prediction analysis, we focus on LncRNAs that have binding sites for PUMILIO, an RBP family involved in post-transcriptional regulation and associated with cancer progression. We compared the expression levels of these LncRNAs in breast cancer and non-tumor samples from the TCGA database. We analyzed the impact of overall and disease-free survival associated with the expression of the LncRNAs and co-expressed genes and targets of PUMILIO proteins. Results: Our results found NORAD as the most relevant LncRNA with a PUMILIO binding site in breast cancer, differently expressed between Luminal A and Basal subtypes. Additionally, NORAD was co-expressed in a Basal-like subtype (0.55) with the RALGAPB gene, a target gene of PUMILIO related to chromosome stability during cell division. Conclusion: These data suggest that this molecular axis may provide insights for developing novel therapeutic strategies for breast cancer.

Self-restricted circular RNA circSOX2 suppressed the malignant progression in SOX2-amplified LUSC

Lung squamous cell carcinoma (LUSC) is a histological subtype of non-small cell lung cancer with the worse progression. SRY-Box Transcription Factor 2 (SOX2) copy number amplification (CNA) is the oncogenic driver in ~60% of patients diagnosed with LUSC. Thus, SOX2 represents an effective therapeutic target in SOX2-amplified LUSC. However, SOX2 protein was considered undruggable. Here, we report the expression of a circular RNA, cicSOX2 in SOX2-amplified LUSC. Patients with SOX2-CAN LUSC expressing circSOX2 manifested increased survival outcomes. CircSOX2 suppressed the proliferation, metastasis, and sphere formation in SOX2-amplified LUSC in vitro and in vivo. CircSOX2 originates in the reverse strand of the SOX2 gene and its sequence was reverse complement to partial 3'UTR of SOX2-coding transcript (mSOX2). CircSOX2 bound to AUF1 and occupied in the 3'UTR of mSOX2, inducing the degradation of mSOX2. In general, circSOX2 is an endogenous self-restricted circRNA in SOX2-amplified LUSC. CircSOX2 might be an effective and stable nucleic acid drug candidate in SOX2-amplified LUSC with low immunogenicity.