Translocations involving ETS family proteins in human cancer

Proteomics analysis reveals novel phosphorylated residues and associated proteins of the polyomavirus DNA replication initiation complex

Polyomavirus ( PyV ) Large T-antigen ( LT ) is the major viral regulatory protein that targets numerous cellular factors/pathways: tumor suppressors, cell cycle regulators, transcription and chromatin regulators, as well as other factors for viral replication. LT directly recruits the cellular replication factors involved in LT's recognition of the viral origin, origin unwinding, and primer synthesis which is carried out by mutual interactions between LT, DNA polymerase alpha-primase ( Polprim ), and single strand (ss) DNA binding replication protein A ( RPA ). The activities as well as interactions of these three with each other as well as other factors, are known to be modulated by post-translational modifications (PTMs); however, modern high-sensitivity proteomic analyses of the PTMs as well as proteins associated with the three have been lacking. Elution from immunoprecipitation (IP) of the three factors were subjected to high-resolution liquid chromatography tandem mass spectrometry (LC-MS/MS). We identified 479 novel phosphorylated amino acid residues (PAARs) on the three factors: 82 PAARs on SV40 LT, 305 on the Polprim heterotetrametric complex and 92 on the RPA heterotrimeric complex. LC-MS/MS analysis also identified proteins that co-immunoprecipitated (coIP-ed) with the three factors that were not previously reported: 374 with LT, 453 with Polprim and 183 with RPA. We used a bioinformatic-based approach to analyze the proteomics data and demonstrate a highly significant "enrichment" of transcription-related process associated uniquely with LT, consistent with its role as a transcriptional regulator, as opposed to Polprim and RPA associated proteins which showed no such enrichment. The most significant cell cycle related network was regulated by ETS proto-oncogene 1 (ETS1), indicating its involvement in regulatory control of DNA replication, repair, and metabolism. The interaction between LT and ETS1 is validated and shown to be independent of nucleic acids. One of the novel phosphorylated aa residues detected on LT from this study, has been demonstrated by us to affect DNA replication activities of SV40 Large T-antigen. Our data provide substantial additional novel information on PAARs, and proteins associated with PyV LT, and the cellular Polprim-, RPA- complexes which will benefit research in DNA replication, transformation, transcription, and other viral and host cellular processes.

Elucidating the importance and regulation of key enhancers for human MEIS1 expression

Myeloid ecotropic virus insertion site 1 (MEIS1) is essential for normal hematopoiesis and is a critical factor in the pathogenesis of a large subset of acute myeloid leukemia (AML). Despite the clinical relevance of MEIS1, its regulation is largely unknown. To understand the transcriptional regulatory mechanisms contributing to human MEIS1 expression, we created a knock-in green florescent protein (GFP) reporter system at the endogenous MEIS1 locus in a human AML cell line. Using this model, we have delineated and dissected a critical enhancer region of the MEIS1 locus for transcription factor (TF) binding through in silico prediction in combination with oligo pull-down, mass-spectrometry and knockout analysis leading to the identification of FLI1, an E-twenty-six (ETS) transcription factor, as an important regulator of MEIS1 transcription. We further show direct binding of FLI1 to the MEIS1 locus in human AML cell lines as well as enrichment of histone acetylation in MEIS1-high healthy and leukemic cells. We also observe a positive correlation between high FLI1 transcript levels and worse overall survival in AML patients. Our study expands the role of ETS factors in AML and our model constitutes a feasible tool for a more detailed understanding of transcriptional regulatory elements and their interactome.

Study on the role of transcription factor SPI1 in the development of glioma

Background

Glioma is a common malignant brain tumor. The purpose of this study was to investigate the role of the transcription factor SPI1 in glioma.

Methods

SPI1 expression in glioma was identified using qRT-PCR and Western blotting. Cell proliferation was assessed using the CCK8 assay. Transwell and wound healing assays were utilized to evaluate cell migration. Additionally, cell cycle and apoptosis were detected using flow cytometry.

Results

We observed that the expression level of SPI1 was up-regulated in glioma tissues, compared to normal tissues. Furthermore, we found that SPI1 is able to promote proliferation and migration of glioma cells in vitro. Flow cytometry results demonstrate that, compared to si-NC cells, si-SPI1 cells stagnated in the G1 phase, and down-regulation of SPI1 expression is able to increase rates of apoptosis. Double luciferase activity and chromatin immunoprecipitation assay results indicated that SPI1 can bind to the promoter sites and promote the proliferation and migration of glioma cells by regulating the expression of oncogenic PAICS.

Conclusions

Our results suggest that SPI1 can promote proliferation and migration of glioma. Furthermore, SPI1 can be utilized as a potential diagnostic marker and therapeutic target for glioma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41016-022-00276-2.

Ubiquitin-Mediated Control of ETS Transcription Factors: Roles in Cancer and Development

Genome expansion, whole genome and gene duplication events during metazoan evolution produced an extensive family of ETS genes whose members express transcription factors with a conserved winged helix-turn-helix DNA-binding domain. Unravelling their biological roles has proved challenging with functional redundancy manifest in overlapping expression patterns, a common consensus DNA-binding motif and responsiveness to mitogen-activated protein kinase signalling. Key determinants of the cellular repertoire of ETS proteins are their stability and turnover, controlled largely by the actions of selective E3 ubiquitin ligases and deubiquitinases. Here we discuss the known relationships between ETS proteins and enzymes that determine their ubiquitin status, their integration with other developmental signal transduction pathways and how suppression of ETS protein ubiquitination contributes to the malignant cell phenotype in multiple cancers.

The role of E26 transformation-specific variant transcription factor 5 in colorectal cancer cell proliferation and cell cycle progression

E26 transformation-specific variant transcription factor 5 (ETV5) contributes to tumor growth and progression and promotes colorectal cancer (CRC) angiogenesis. Previous studies indicate that ETV5 may regulate the cell cycle, but its detailed mechanism remain unclear. Gene Ontology (GO) analysis of RNA-seq data revealed that ETV5 possibly regulates the cell cycle in CRC. Here, in vitro and in vivo experiments were performed to verify that ETV5 promoted tumor progression and influenced cell cycle G1/S transition. Cell cycle PCR array and co-immunoprecipitation (Co-IP) helped identify the p21-CDKs pathway. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were performed to determine whether ETV5 binds to the p21 promoter. ETV5 and p21 were detected by immunohistochemistry, and the effects of their expression on CRC patients were evaluated. ETV5 upregulation enhanced tumor proliferative capacity and promoted G1 phase transfer to the S phase. ETV5 knockdown slowed the growth of CRC cells and repressed the G1/S transition. We also found p21 as a downstream target of ETV5. p21 knockdown resulted in faster CRC cell growth and in more cells being driven from the G0/1 phase into the S phase. Co-IP experiments showed that p21 banding to CDK2, CDK4, and CDK6 inhibited p130 phosphorylation. Using the ChIP and luciferase reporter assay, we confirmed that ETV5 bound to the p21 promoter and repressed p21 expression. CRC patients with high ETV5 expression and low p21 expression showed the worst prognosis. Finally, by targeting p21 to regulate CDK function, ETV5 also changed drug-sensitivity to palbociclib and dinaciclib. In conclusion, ETV5 promoted cell cycle G1/S transition through transcriptional inhibition of p21, thereby accelerating tumor growth. Moreover, ETV5 changed drug-sensitivity to palbociclib and dinaciclib. Therefore, therapeutic regimens targeting ETV5 may be promising in improving the efficacy of target-CDK treatment in CRC.

Hsa_circRNA_000166 Promotes Cell Proliferation, Migration and Invasion by Regulating miR-330-5p/ELK1 in Colon Cancer

INTRODUCTION

Circular RNAs (circRNAs), a novel class of non-coding RNAs, which are widely expressed in human cells, have essential roles in the development and progression of cancers. The aim of this study is to figure out the role of circ_000166 in colon cancer (CC) development and the signaling pathway involved.

MATERIALS AND METHODS

HT29 and HCT116 cells were transfected with siRNA of circRNA, miRNA mimics and inhibitors. Cell proliferation, migration and invasion were examined using CCK-8 assay and transwell assay, respectively. Luciferase reporter assay was used to validate the targets of circRNA and miRNA. CC cells were implanted into nude mice subcutaneously to detect tumor growth.

RESULTS

hsa_circRNA_000166 was significantly upregulated in the human CC tissue and in the CC cell lines. Knockdown of hsa_circRNA_000166 reduced cell viability, colony formation, migration and invasion in vitro and decreased tumor size and weight in vivo. Luciferase reporter assay revealed that miR-330-5p was the target of circRNA_000166. miR-330-5p could bind to 3' untranslated region (3'UTR) of ELK1 to downregulate both mRNA and protein expression of ELK1. Dual inhibition of circRNA_000166 and miR-330-5p inhibited the suppression of cell proliferation, migration and invasion induced by si-circRNA_000166.

CONCLUSION

The data of this study demonstrated that the hsa_circRNA_000166 could upregulated the expression of gene ELK1 by sponging miR-330-5p, which may contribute to a better understanding of the regulatory circRNA/miRNA/mRNA network and CC pathogenesis.