Elena Kashuba Project

EBNA-binding cellular proteins and their role in cell transformation

The discovery of molecular mechanisms of cell transformation is one of the most important and intricate questions of modern cell biology. We are using the Epstein-Barr virus (EBV)-induced B-cell immortalization as a model system. It is clear now that EBV exploits the normal signaling pathways of the B lymphocyte and the six growth transformation associated EBNAs promote cell proliferation and protect from apoptosis. Our project is aimed on elucidation of the role of cellular proteins that bind to EBNAs in cell transformation.

Over the last few years, we have discovered 17 previously unknown interactions between three transforming proteins - EBNA-3, EBNA-5 and EBNA-6 and cellular proteins.

Recently we have shown that trimolecular protein complexes of EBNA-5, MDM2, and p53 were formed, where MDM2 served as a bridge. EBNA-5 inhibited MDM2-dependent polyubiquitination (but not monoubiquitination) and degradation of p53 in vitro. These findings indicate that the high p53 levels in LCL are due to EBNA-5 dependent inhibition of p53 degradation. Tri-molecular complex formation prevents binding of p53 to DNA, and thereby inactivates the p53 dependent apoptotic pathway. We have also found that EBNA-3 protects LCL from VDR-induced apoptosis due to the binding to VDR that represses the transcription of VDR target genes.

We have discovered that the HIF1A protein is stabilized in EBV transformed B-cells, in contrast to mitogen activated B-cells. Lymphoblastoid cells use both the aerobic, oxidative, and non aerobic, glycolytic pathways for energy production, even in the presence of abundant oxygen, thus resemble most solid tumors with regard to the 'Warburg effect'.

Studying the influence of EBV on the RB  E2F1 pathway, we have found that EBNA-6 interacts with RB-associated protein, mitochondrial ribosomal protein MRPS18-2 (S18-2), leading to the liberation of E2F1. This stimulates the entry of the cell into the S-phase.

Unexpectedly, overexpression of S18-2 protein in the primary rat embryonic fibroblasts (REFs) led to REF immortalization. A derived cell line (18IM) expressed the embryonic stem cell markers SSEA-1 and Sox2. Pathways involved in oxidative phosphorylation, ubiquinone (Coenzyme Q 10) biosynthesis, fatty acid elongation in mitochondria, PI3K/AKT signaling, a characteristic of rapidly proliferating cells, were upregulated in 18IM. Genes involved in the transcription/translation machinery and redox reactions were upregulated as well. 18IM cells produced more pyruvate, indicating enhanced ATP synthesis.

We are currently investigating the role of S18-2 protein in cell immortalization and embryogenesis. We would like to characterize novel pathways of cell fate regulation and to identify the new putative diagnostic and/or prognostic markers of cancerogenesis.


The European meeting on epstein barr virus and associated malignances took place in June 2015

View the program on the website and the book of abstracts

Elena Kashuba Publications

S18 family of mitochondrial ribosomal proteins: evolutionary history and Gly132 polymorphism in colon carcinoma.
Mushtaq M, Ali R, Kashuba V, Klein G, Kashuba E
Oncotarget 2016 Jul;():

Role of the RB-Interacting Proteins in Stem Cell Biology.
Mushtaq M, Gaza H, Kashuba E
Adv. Cancer Res. 2016 ;131():133-57

Mitochondrial ribosomal protein S18-2 is highly expressed in endometrial cancers along with free E2F1.
Mints M, Mushtaq M, Iurchenko N, Kovalevska L, Stip M, Budnikova D, et al
Oncotarget 2016 Apr;7(16):22150-8

DNA Tumor Viruses and Cell Metabolism.
Mushtaq M, Darekar S, Kashuba E
Oxid Med Cell Longev 2016 ;2016():6468342

Different Mechanisms of Regulation of the Warburg Effect in Lymphoblastoid and Burkitt Lymphoma Cells.
Mushtaq M, Darekar S, Klein G, Kashuba E
PLoS ONE 2015 ;10(8):e0136142

Mitochondrial ribosomal protein S18-2 evokes chromosomal instability and transforms primary rat skin fibroblasts.
Darekar S, Mushtaq M, Gurrapu S, Kovalevska L, Drummond C, Petruchek M, et al
Oncotarget 2015 Aug;6(25):21016-28

Epstein-Barr virus immortalization of human B-cells leads to stabilization of hypoxia-induced factor 1 alpha, congruent with the Warburg effect.
Darekar S, Georgiou K, Yurchenko M, Yenamandra S, Chachami G, Simos G, et al
PLoS ONE 2012 ;7(7):e42072

Stem cell gene expression in MRPS18-2-immortalized rat embryonic fibroblasts.
Yenamandra S, Darekar S, Kashuba V, Matskova L, Klein G, Kashuba E
Cell Death Dis 2012 Jan;3():e357

Epstein-Barr virus encoded EBNA-3 binds to vitamin D receptor and blocks activation of its target genes.
Yenamandra S, Hellman U, Kempkes B, Darekar S, Petermann S, Sculley T, et al
Cell. Mol. Life Sci. 2010 Dec;67(24):4249-56

Epstein-Barr virus-encoded EBNA-5 forms trimolecular protein complexes with MDM2 and p53 and inhibits the transactivating function of p53.
Kashuba E, Yurchenko M, Yenamandra S, Snopok B, Szekely L, Bercovich B, et al
Int. J. Cancer 2011 Feb;128(4):817-25

Euroethics--a database network on biomedical ethics.
Gavel Y, Andersson P, Knutssøn G
Health Info Libr J 2006 Sep;23(3):169-78

Interaction of Epstein-Barr virus (EBV) with human B-lymphocytes.
Klein G, Klein E, Kashuba E
Biochem. Biophys. Res. Commun. 2010 May;396(1):67-73


Full Publication List

All Elena Kashuba Publications on Pub Med

Further Publications (Pdf file, 146 Kb)

Project Group Members

Senior researcher

Elena Kashuba

Phone: 08-524 862 59
Organizational unit: Marie Arsenian Henriksson group
E-mail: Elena.Kashuba@ki.se

Elena Kashuba CV

Graduate Student

Muhammad Mushtaq

Organizational unit: George Klein group
E-mail: muhammad.mushtaq@ki.se

Muhammad Mushtaq CV


Photo Archive of Group Members 

Photo Archive (Pdf file, 6 Mb)

Visiting researchers:

Master students:

  • Suhas Darekar, Skövde University, Sweden (2008)
  • Anna-Katharina Schulsche, Marburg University, Germany (2008-2009)
  • Konstantinos Georgiou, University of Montpellier 2, France (2010-2011))
  • Chen Meng, Royal Institute of Technology (KTH) (2011)
  • Sreeharsha Gurrapu, Hyderabad University, India (2011-2012)
  • Mariia Petruchek, Taras Shevchenko State University, Kyiv, Ukraine (2012-2013)
  • Valdemar Priebe, KI (2012)
  • Milos Goikovic, KI (2012-2013)


Collaborations (Pdf file, 60 Kb)

Tumour BiologyVirology