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Εργαστήριο Χρονοβιολογίας

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Research Staff

Anastasia Prombona, Researcher Β΄

Anastasia Repouskou, Postdoctoral Researcher

Angeliki Galeou, Postgraduate Student (PhD)

Marios Xydous, Postdoctoral Researcher (50% of his time)

K. Koutourlou, Biology Student, Summer practice

Research Interests of the Lab

Investigation of the biological clock function in plants

Study of rhythmically expressed genes in Phaseolus vulgaris. Involvement of white and monochromatic light and photoperiodism in the synchronization of the clock. Oscillator function in Phaseolus vulgaris.

Interaction of the biological clock with pathological processes

Interaction of circadian clock components with the oncoprotein c-MYC. Regulation of oncoprotein expression by the biological clock, from transcription to protein accumulation level. Correlation of gene expression levels with epigenetic changes at the promoter region. Study of biological rhythms in lymphocytes of patients with psychiatric disorders.

2014 Findings

Investigation of the biological clock function in plants

In order to explore the function of central oscillator elements in P. vulgaris, we cloned the upstream region ~2000 bases in length of the open reading frame (ORF) of three rhythmically expressed clock genes, namely PvLHY, PvTOC1 and PvELF4. Luciferase (Luc) measurements driven by truncated promoter fragments showed that for PvTOC1 1100 bases of the region upstream of the ATG start codon are sufficient to drive Luc expression.  In the case of PvELF4 the -1450 bases region drives highest levels of Luc expression, while 2000 bases of the PvLHY upstream region constitute a weak promoter. Mutagenesis of putative cis motifs is ongoing in order to identify regulatory elements involved in circadian and light driven expression. Moreover, cloning of PvLHY, PvTOC1 and PvELF4 ORFs in plant expression vectors is in progress in order to explore their role in P. vulgaris clock function. The study of all mentioned constructs is accomplished in bean protoplasts (A. Galeou and A. Prombona, unpublished).

Figure 1: Bean protoplasts isolated from leaves are transformed at high efficiency (picture left: expression of green fluorescent protein) and retain rhythmic expression of clock genes (graph right).

Interaction of the biological clock with pathological processes

  1. A. Interaction of the biological clock with carcinogenesis.

Several studies from the clinical oncology report circadian rhythm disruption in cancer tissue. Deciphering the molecular mechanism that governs this phenomenon is under investigation in many laboratories. Our group investigates the interaction of the oncoprotein c-ΜYC with elements of the central oscillator in malignant cell lines. Our results strongly indicate that at overexpressed levels, a situation that is observed in cancer cells, c-MYC interferes with circadian driven transcription independently of its role as a transcription factor (A. Repouskou and A. Prombona, manuscript in preparation).

B. Interaction of the biological clock with pathological processes.

In a previous work we had shown that the acute response induced by the glucocorticoid dexamethasone of the mouse central clock gene per1 (mper1) can be blocked by nicotinamide (NAM), a metabolic molecule which has been shown to possess anxiolytic properties. This inhibition is accompanied by reduced histone H3 trimethylation of lysine 4 (H3K4me3) in the mper1 promoter. Our further studies have documented that NAM additionally inhibits the acute response of serum glucocorticoid kinase 1 (Sgk1), a non-clock but glucocorticoid responsive gene.  This is also accompanied by reduction of sgk mRNA levels and of the abundance of H3K4me3 and H3K9/14ac in the gene’s promoter. These results clarify partly the molecular mechanisms in respect to histone epigenetics of the acute response of the studied genes to dexamethasone and the role of NAM.

Another ongoing project deals with the study of daily rhythms in the lymphocytes of peripheral blood from persons with psychotic disorders. As lymphocytes reflect pathologies of the brain, we compare with rhythms from lymphocytes of healthy people of the same age group, in order to find out whether we can correlate the pathological status with circadian clock disorders. These projects are performed by Dr. M. Xydous in collaboration with Dr. T. Sourlingas.

Publications 2014

Xydous M, Prombona A, Sourlingas TG. (2014). The role of H3K4me3 and H3K9/14ac in the induction by dexamethasone of Per1 and Sgk1, two glucococorticoid early response genes that mediate the effects of acute stress in mammals. Biochim Biophys Acta 1839(9):866-72.  Impact factor 5.44

Conferences 2014

Anastasia Repouskou and Anastasia Prombona (2014) Circadian clock regulates c-MYC protein stability via rhythmic acetylation. FEBS–EMBO 2014 Conference, 30 August – 4 September 2014, Paris, France FEBS Journal 281 (Suppl. 1) CSII-03 – Circadian Clocks p. 258

Anastasia Repouskou and Anastasia Prombona (2014) A novel role for c-MYC oncoprotein in the regulation of circadian gene promoters. 65th Congress of the Hellenic Society of Biochemistry and Molecular Biology, 28th-30th November 2014, Thessaloniki, Poster Session P145

Angeliki Galeou and Anastasia Prombona (2014) Functional analysis of Phaseolus vulgaris putative core clock genes. 65th Congress of the Hellenic Society of Biochemistry and Molecular Biology, 28th-30th November 2014, Thessaloniki, Poster Session P32


Supervision of PhD work of graduate student A. Galeou

Member of the scientific committee for the supervision of the PhD thesis of A. Galeou in the Biology Department of the National Kapodistrian University of Athens.

Supervision of the practical exercise of the student K. Koutourlou from the University of Patras.

Other Scientific Activities

Reviewer of Plant Cell Reports article

Other activities in IB-A

Member in charge for the presentation of IB-E to students.

Impact factor (for 1 publication) : 5.44

Citations 2014 (self citations excluded): 8

Citations 2010-2014 (self citations excluded): 40 h-factor: 7

Lab equipment (ΙΒ-Ε)

Thermal Cycler 2 blocks (Biorad)

Thermal Cycler (MJ Reasearch)

Electroporator (BTX, ECM 399)

Hybridization Oven (Stuart Scientific)

Spectrophotometer (Hitachi)

French Press (Aminco)

Incubator 37oC (Gallenkamp)


External Funding



Funding amount total: 150 000 €

Total funding of the Lab: 60 000 €

Funding for 2014: 60 000 €.