Cloning the human SUMO1 promoter

ERα promotes SUMO1 transcription by binding with the ERE and enhances SUMO1-mediated protein SUMOylation in breast cancer

Background

Estrogen plays a crucial role in the tumorigenesis of breast cancer (BC), and epigenetic modification by SUMOylation is essential for cancer development. However, the mechanism underlying estrogen's actions on protein SUMOylation and its effect on BC development are still incompletely understood.

Methods

SUMO1 in BC cell lines was verified via real-time quantitative PCR (RT-qPCR) and western blot. Cell proliferation and colony formation assays was also performed to evaluate SUMOylation as mediated by SUMO1. Luciferase activity to examine whether E2 promoted the transcription of SUMO1, and chromatin immunoprecipitation (ChIP) assay to determine the binding of estrogen receptor alpha (ERα) to SUMO1 were conduction, and an animal model was used to evaluate the effects of E2-ERα-enhanced SUMO1 transcription.

Results

E2 promoted SUMO1 mRNA and protein expression levels in a dose- and time-dependent manner in ER-positive BC cells; it exerted no influence on SUMO2/3 expression; in E2-induced SUMO1 transcription, ERα, but not ERβ, was essential to the process. In addition, E2-ERα upregulated the transcription of SUMO1 by binding with an estrogen-response element half-site (1/2ERE, in the -134 to -123 bp region) of the SUMO1 promoter, and E2-ERα induced SUMO1 transcription-enhanced cellular viability in ER-positive BC cells. To further determine SUMOylation as mediated by SUMO1 in ER-positive BC, we evaluated novel SUMO1 target proteins such as Ras and demonstrated that E2 increased Ras SUMOylation and cellular proliferation by affecting downstream signaling-pathway transduction. Finally, our data revealed that E2-ERα enhanced SUMO1 transcription to promote tumor growth in a BC orthotopic tumor model.

Conclusions

Collectively, our results showed that E2 promoted the transcription and protein expression of SUMO1 via ERα binding to a 1/2ERE in the SUMO1 promoter, and that E2-ERα also augmented SUMO1-mediated Ras SUMOylation and mediated cellular responses in ER-positive BC. We therefore achieved significant insights into the mechanism involved in ER-positive BC development and provided a novel target for its treatment.

Epstein-Barr Virus Latent Membrane Protein-1 Induces the Expression of SUMO-1 and SUMO-2/3 in LMP1-positive Lymphomas and Cells

Epstein-Barr Virus latent membrane protein-1 (LMP1) interacts with the SUMO-conjugating enzyme Ubc9, which induces protein sumoylation and may contribute to LMP1-mediated oncogenesis. After analyzing human lymphoma tissues and EBV-positive cell lines, we now document a strong correlation between LMP1 and sumo-1/2/3 or SUMO-1/2/3 levels, and show that LMP1-induced sumo expression requires the activation of NF-κB signaling through CTAR1 and CTAR2. Together, these results point to a second mechanism by which LMP1 dysregulates sumoylation processes and adds EBV-associated lymphomas to the list of malignancies associated with increased SUMO expression.

Rhabdoviruses, Antiviral Defense, and SUMO Pathway

Small Ubiquitin-like MOdifier (SUMO) conjugation to proteins has essential roles in several processes including localization, stability, and function of several players implicated in intrinsic and innate immunity. In human, five paralogs of SUMO are known of which three are ubiquitously expressed (SUMO1, 2, and 3). Infection by rhabdoviruses triggers cellular responses through the activation of pattern recognition receptors, which leads to the production and secretion of interferon. This review will focus on the effects of the stable expression of the different SUMO paralogs or Ubc9 depletion on rhabdoviruses-induced interferon production and interferon signaling pathways as well as on the expression and functions of restriction factors conferring the resistance to rhabdoviruses.

Viral manipulation of the cellular sumoylation machinery

Viruses exploit various cellular processes for their own benefit, including counteracting anti-viral responses and regulating viral replication and propagation. In the past 20 years, protein sumoylation has emerged as an important post-translational modification that is manipulated by viruses to modulate anti-viral responses, viral replication, and viral pathogenesis. The process of sumoylation is a multi-step cascade where a small ubiquitin-like modifier (SUMO) is covalently attached to a conserved ΨKxD/E motif within a target protein, altering the function of the modified protein. Here we review how viruses manipulate the cellular machinery at each step of the sumoylation process to favor viral survival and pathogenesis.