EIYMNVPV Motif is Essential for A1CF Nucleus Localization and A1CF (-8aa) Promotes Proliferation of MDA-MB-231 Cells via Up-Regulation of IL-6

Genetic alteration of mRNA editing enzyme APOBEC3B in the pathogenesis of ovarian endometriosis

RESEARCH QUESTION

What are the specific genetic alterations and associated network in endometriotic cells responsible for the disease pathogenesis?

DESIGN

Case control experimental study involving 45 women with endometriosis who underwent laparoscopic surgery (case) and 45 normal samples from women undergoing total abdominal hysterectomy (control). The endometrial samples were subjected to whole exome sequencing (WES) of endometriotic tissue and copy number variation analysis. Validation of gene hits were obtained from WES using polymerase chain reaction techniques, immunological techniques, in-silico tools and transgenic cell line models.

RESULTS

Germline heterozygous deletion of mRNA editing enzyme subunit APOBEC3B was identified in about 96% of endometriosis samples. The presence of germline deletion was confirmed with blood, endometrium and normal ovary samples obtained from the same patient. APOBEC3B deletions resulted in a hybrid protein that activates A1CF. APOBEC3B deletion can be a major cause of changes in the endometriotic microenvironment, and contributes to the pathogenesis and manifestation of the disease. The effect of APOBEC3B deletion was proved by in-vitro experiments in a cell line model, which displayed endometriosis-like characteristics. APOBEC3B germline deletion plays a major role in the pathogenesis of endometriosis, which is evident by the activation of A1CF, an increase in epithelial to mesenchymal transition, cellular proliferation, inflammation markers and a decrease in apoptosis markers.

CONCLUSION

The deleterious effects caused by APOBEC3B deletion in endometriosis were identified and confirmed. These results might provide a base for identifying the complete pathogenetic mechanism of endometriosis, thereby moving a step closer to better diagnosis and treatment options.

A1CF Binding to the p65 Interaction Site on NKRF Decreased IFN-β Expression and p65 Phosphorylation (Ser536) in Renal Carcinoma Cells

Apobec-1 complementation factor (A1CF) functions as an RNA-binding cofactor for APO-BEC1-mediated C-to-U conversion during RNA editing and as a hepatocyte-specific regulator in the alternative pre-mRNA splicing of metabolic enzymes. Its role in RNA editing has not been clearly established. Western blot, co-immunoprecipitation (Co-IP), immunofluorescence (IF), methyl thiazolyl tetrazolium (MTT), and 5-ethynyl-2'-deoxyuridine (EdU) assays were used to examine the role of A1CF beyond RNA editing in renal carcinoma cells. We demonstrated that A1CF interacts with NKRF, independent of RNA and DNA, without affecting its expression or nuclear translocation; however, it modulates p65(Ser536) phosphorylation and IFN-β levels. Truncation of A1CF or deletion on NKRF revealed that the RRM1 domain of A1CF and the p65 binding motif of NKRF are required for their interaction. Deletion of RRM1 on A1CF abrogates NKRF binding, and the decrease in IFN-β expression and p65(Ser536) phosphorylation was induced by A1CF. Moreover, full-length A1CF, but not an RRM1 deletion mutant, promoted cell proliferation in renal carcinoma cells. Perturbation of A1CF levels in renal carcinoma cells altered anchorage-independent growth and tumor progression in nude mice. Moreover, p65(Ser536) phosphorylation and IFN-β expression were lower, but ki67 was higher in A1CF-overexpressing tumor tissues of a xenograft mouse model. Notably, primary and metastatic samples from renal cancer patients exhibited high A1CF expression, low p65(Ser536) phosphorylation, and decreased IFN-β levels in renal carcinoma tissues compared with the corresponding paracancerous tissues. Our results indicate that A1CF-decreased p65(Ser536) phosphorylation and IFN-β levels may be caused by A1CF competitive binding to the p65-combined site on NKRF and demonstrate the direct binding of A1CF independent of RNA or DNA in signal pathway regulation and tumor promotion in renal carcinoma cells.

Regulatory roles of RNA modifications in breast cancer

Collectively referred to as the epitranscriptome, RNA modifications play important roles in gene expression control regulating relevant cellular processes. In the last few decades, growing numbers of RNA modifications have been identified not only in abundant ribosomal (rRNA) and transfer RNA (tRNA) but also in messenger RNA (mRNA). In addition, many writers, erasers and readers that dynamically regulate the chemical marks have also been characterized. Correct deposition of RNA modifications is prerequisite for cellular homeostasis, and its alteration results in aberrant transcriptional programs that dictate human disease, including breast cancer, the most frequent female malignancy, and the leading cause of cancer-related death in women. In this review, we emphasize the major RNA modifications that are present in tRNA, rRNA and mRNA. We have categorized breast cancer-associated chemical marks and summarize their contribution to breast tumorigenesis. In addition, we describe less abundant tRNA modifications with related pathways implicated in breast cancer. Finally, we discuss current limitations and perspectives on epitranscriptomics for use in therapeutic strategies against breast and other cancers.

APOBEC1 complementation factor facilitates cell migration by promoting nucleus translocation of SMAD3 in renal cell carcinoma cells

Metastasis is inevitable in about 30% of patients with primary renal cell carcinoma after nephrectomy treatment. APOBEC1 complementation factor (A1CF), an RNA binding protein, participates in tumor progressions such as growth, apoptosis, differentiation, and invasion. Here, we explored biological functions of A1CF and provided a new insight into renal cell carcinoma metastasis. Wound healing assay was conducted to detect migration in A1CF overexpression and knockdown stable cell lines. Quantitative PCR and western blot assays were utilized to test transcriptional and translation levels of A1CF and SMAD3 in A1CF overexpression and knockdown renal carcinoma cells. Nuclear and cytoplasmic protein separation assays were conducted to evaluate the subcellular distribution of A1CF and SMAD3. Immunoprecipitation assay was conducted to detect the interaction between A1CF and SMAD3. Our study demonstrated A1CF overexpression facilitated cell migration in renal carcinoma cells. A1CF deficiency downregulated expression of SMAD3, Snail1, and N-cadherin. In addition, A1CF promoted nucleus translocation of SMAD3 and interacted with SMAD3. SMAD3 knockdown attenuated cell migration induced by A1CF overexpression. Our study suggested A1CF facilitated cell migration by promoting nucleus translocation of SMAD3 in renal cell carcinoma cells.

High APOBEC1 Complementation Factor Expression Positively Modulates the Proliferation, Invasion, and Migration of Endometrial Cancer Cells Through Regulating P53/P21 Signaling Pathway

Background: APOBEC1 complementation factor (A1CF) is a component of the apolipoprotein-B messenger RNA editing complex that participates in various cellular processes and acts as an oncogene in many cancers. In this study, it was aimed to investigate the roles of A1CF and its potential mechanism in endometrial cancer (EC). Materials and Methods: Gene expression prolife was downloaded from The Cancer Genome Atlas database. Then Kaplan-Meier and Cox regression analyses were conducted to assess the prognostic value of A1CF in EC. Cell Counting Kit-8, plate clone formation, and transwell assays were used to estimate the functions of A1CF on the proliferation, invasion, and migration of EC cell. The gene set enrichment analysis was used to analyze the pathway that is enriched by A1CF, whereas quantitative real-time polymerase chain reaction and Western blot analyses were utilized to detect the mRNA and protein expression involved. Results: It was detected that the upregulated A1CF was enriched in P53/P21 signaling pathway and tightly associated with patients' age, stage, and death. Besides, high A1CF expression led to a shorter overall survival of patients and predicted a poor prognosis in EC. The overexpression of A1CF promoted the proliferation, invasion, and migration of EC cells, whereas the depletion of A1CF suppressed these processes. Moreover, P21 and P53 were reduced whereas cyclin D1 and proliferating cell nuclear antigen were induced along with the increasing of A1CF. However, the effects of silencing A1CF on these protein expressions were on the contrary. Conclusion: A1CF was highly expressed and closely related to the prognosis and progression of EC through the regulation of P53/P21 signaling pathway, providing a possible new therapy target site for EC.

Inhibition of the aberrant A1CF-FAM224A-miR-590-3p-ZNF143 positive feedback loop attenuated malignant biological behaviors of glioma cells

Background

Glioma is the most common and lethal type of malignant brain tumor. Accumulating evidence has highlighted that RNA binding protein APOBEC1 complementation factor (A1CF) is involved in various cellular processes by modulating RNA expression, and acts as an oncogene in breast cancer. However, the function of A1CF in glioma remained unclear.

Methods

Quantitative RT-PCR and western blot analysis were employed to detect the expression levels of A1CF, lncRNA family with sequence similarity 224 member A (FAM224A), miR-590-3p, zinc finger protein 143 (ZNF143) and ArfGAP with SH3 domain, ankyrin repeat and PH domain 3 (ASAP3) in glioma tissues and cell lines. The Cell Counting Kit-8 assay, migration and invasion assays, and flow cytometry analysis were conducted to evaluate the function of A1CF, FAM224A, miR-590-3p, ZNF143 and ASAP3 in the malignant biological behaviors of glioma cells. Moreover, luciferase reporter, RIP and ChIP assays were used to investigate the interactions among A1CF, FAM224A, miR-590-3p, ZNF143, ASAP3 and MYB. Finally, the xenograft tumor growth assay further ascertained the biological roles of A1CF, FAM224A and miR-590-3p in glioma cells.

Results

A1CF was upregulated and functioned as an oncogene via stabilizing and increasing FAM224A expression; moreover, high A1CF and FAM224A expression levels indicated a poorer prognosis for glioma patients. Conversely, miR-590-3p was downregulated and exerted a tumor-suppressive function in glioma cells. Inhibition of A1CF significantly restrained cell proliferation, migration and invasion, and promoted apoptosis by upregulating miR-590-3p in a FAM224A-dependent manner. FAM224A was a molecular sponge of miR-590-3p and they were in an RNA-induced silencing complex. ZNF143 was upregulated in glioma tissues and cell lines. MiR-590-3p could negatively modulate the expression of ZNF143 via binding to the ZNF143 3′ UTR. Moreover, ZNF143 participated in miR-590-3p-induced tumor-suppressive activity on glioma cells. ASAP3 and MYB were transcriptionally activated by ZNF143, and importantly, ZNF143 could directly target the promoter of FAM224A and stimulate its expression, collectively forming a positive feedback loop.

Conclusions

The present study clarifies that the A1CF-FAM224A-miR-590-3p-ZNF143 positive feedback loop conducts critical regulatory effects on the malignant progression of glioma cells, which provides a novel molecular target for glioma therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1200-5) contains supplementary material, which is available to authorized users.

A1CF-Axin2 signal axis regulates apoptosis and migration in Wilms tumor-derived cells through Wnt/β-catenin pathway

A1CF, a complementary factor of APOBEC-1, is involved in many cellular processes for its mRNA editing role, such as cell proliferation, apoptosis, and migration. Here, we explored the regulatory function of A1CF in Wilms tumor-derived cells. Quantitative real-time PCR was performed to detect the mRNA level of A1CF, Axin2, β-Catenin, CCND1 or NKD1 in A1CF-depleted or A1CF-overexpression G401 cells. Western bolt was used to analyze the expression of A1CF, Axin2, and β-catenin protein. The cell apoptosis and migration ability were determined using flow cytometry assay or wound healing, respectively. Our study demonstrated that overexpression of A1CF, Axin2 was upregulated and knockdown of A1CF decreased Axin2 expression at mRNA and protein levels in G401 cells. Besides, knockdown of A1CF further upregulated β-catenin, the classical regulator of Wnt signal pathway, and increased CCND1 and NKD1, the target genes of Wnt/β-catenin. Furthermore, overexpression of Axin2 partly rescued the expression of β-catenin in A1CF-deficiency stable G401 cells. In Wnt agonist BML-284 treated G401 cells, A1CF was increased like other classical regulator of Wnt signal pathway, such as Axin2 and β-catenin. Meanwhile, knockdown of Axin2 rescued β-catenin expression which was decreased in A1CF overexpression condition with BML-284. Further, overexpression of A1CF reduced cell apoptosis but promoted cell migration, and overexpression of Axin2 got similar results. In A1CF-decreased stable G401 cells, overexpression of Axin2 partly rescued the cell apoptosis and migration. We find that A1CF is a positive regulator of Axin2, a Wnt/β-catenin pathway inhibitor, and A1CF-Axin2 signal axis regulates Wilms tumor-derived cells' apoptosis and migration through Axin2.