p113 isoform encoded by CUX1 circular RNA drives tumor progression via facilitating ZRF1/BRD4 transactivation

Mol Cancer. 2021 Sep 27;20(1):123. doi: 10.1186/s12943-021-01421-8.

Abstract

Background: Metabolic reprogramming sustains tumorigenesis and aggressiveness of neuroblastoma (NB), the most common extracranial malignancy in childhood, while underlying mechanisms and therapeutic approaches still remain elusive.

Methods: Circular RNAs (circRNAs) were validated by Sanger sequencing. Co-immunoprecipitation, mass spectrometry, chromatin immunoprecipitation (ChIP) sequencing, and RNA sequencing assays were applied to explore protein interaction and target genes. Gene expression regulation was observed by ChIP, dual-luciferase reporter, real-time quantitative RT-PCR, and western blot assays. Gain- and loss-of-function studies were performed to observe the impacts of circRNA-encoded protein and its partners on the lipid metabolism, mitochondrial activity, growth, invasion, and metastasis of NB cells.

Results: A novel 113-amino acid protein (p113) of CUT-like homeobox 1 (CUX1) was identified in NB cells treated by serum deprivation. Further validating studies revealed that nuclear p113 was encoded by circRNA of CUX1, and promoted the lipid metabolic reprogramming, mitochondrial activity, proliferation, invasion, and metastasis of NB cells. Mechanistically, p113 interacted with Zuotin-related factor 1 (ZRF1) and bromodomain protein 4 (BRD4) to form a transcriptional regulatory complex, and mediated the transactivation of ZRF1/BRD4 in upregulating ALDH3A1, NDUFA1, and NDUFAF5 essential for conversion of fatty aldehydes into fatty acids, fatty acid β-oxidation, and mitochondrial complex I activity. Administration of an inhibitory peptide blocking p113-ZRF1 interaction suppressed the tumorigenesis and aggressiveness of NB cells. In clinical NB cases, high expression of p113, ZRF1, or BRD4 was associated with poor survival of patients.

Conclusions: These results indicate that p113 isoform encoded by CUX1 circular RNA drives tumor progression via facilitating ZRF1/BRD4 transactivation.

Keywords: Bromodomain protein 4; Circular RNA-coding protein; Neuroblastoma progression; Zuotin-related factor 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomarkers, Tumor
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Disease Models, Animal
  • Disease Progression
  • Fatty Acids / metabolism
  • Gene Editing
  • Gene Expression Regulation, Neoplastic*
  • Heterografts
  • Homeodomain Proteins / chemistry
  • Homeodomain Proteins / genetics*
  • Humans
  • Lipid Metabolism
  • Mice
  • Mitochondria / genetics
  • Mitochondria / metabolism
  • Models, Biological
  • Models, Molecular
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism*
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Neoplasms / mortality
  • Neoplasms / pathology
  • Oxidation-Reduction
  • Peptides / chemistry
  • Peptides / pharmacology
  • Prognosis
  • Protein Binding / drug effects
  • Protein Isoforms
  • RNA, Circular / genetics*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Repressor Proteins / chemistry
  • Repressor Proteins / genetics*
  • Stress, Physiological
  • Structure-Activity Relationship
  • Transcription Factors / chemistry
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism*
  • Transcriptional Activation*

Substances

  • BRD4 protein, human
  • Biomarkers, Tumor
  • CUX1 protein, human
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • DNAJC2 protein, human
  • Fatty Acids
  • Homeodomain Proteins
  • Molecular Chaperones
  • Peptides
  • Protein Isoforms
  • RNA, Circular
  • RNA-Binding Proteins
  • Repressor Proteins
  • Transcription Factors