UVA irradiation strengthened an interaction between UBF1/2 proteins and H4K20 di-/tri-methylation

  • Lenka Stixová
  • Denisa Komůrková
  • Alena Svobodová Kovaříková
  • Eva Bártová
Original Article


Repair of ribosomal DNA (rDNA) is a very important nuclear process due to the most active transcription of ribosomal genes. Proper repair of rDNA is required for physiological biogenesis of ribosomes. Here, we analyzed the epigenetics of the DNA damage response in a nucleolar compartment, thus in the ribosomal genes studied in nonirradiated and UVA-irradiated mouse embryonic fibroblasts (MEFs). We found that the promoter of ribosomal genes is not abundant on H4K20me2, but it is densely occupied by H4K20me3. Ribosomal genes, regulated via UBF1/2 proteins, were characterized by an interaction between UBF1/2 and H4K20me2/me3. This interaction was strengthened by UVA irradiation that additionally causes a focal accumulation of H4K20me3 in the nucleolus. No interaction has been found between UBF1/2 and H3K9me3. Interestingly, UVA irradiation decreases the levels of H3K9me3 and H4K20me3 at 28S rDNA. Altogether, the UVA light affects the epigenetic status of ribosomal genes at 28S rDNA and strengthens an interaction between UBF1/2 proteins and H4K20me2/me3.


DNA repair UVA irradiation Nucleolus UBF DNA damage response 



Ataxia telangiectasia mutated


ATM and Rad3 related


Chromatin immunoprecipitation


Cyclobutane pyrimidine dimers


DNA damage response


Dense fibrillar compartment


Dulbecco’s modified Eagle’s medium


Double-strand breaks


Fibrillar centers


Fluorescence-lifetime imaging microscopy


Förster resonance energy transfer


Granular component


Green fluorescence protein


Global genome NER


Tri-methylated lysine 9 of histone H3


Tri-methylated/di-methylated lysine 20 of histone H4


Homologous recombination


Mouse embryonic fibroblasts


Nijmegen breakage syndrome


Nucleotide excision repair


Nonhomologous end joining


Nucleolar organizer regions


Phosphate-buffered saline


Polymerase chain reaction


Posttranslational modifications


Ribosomal DNA


RNA polymerase I/II


Ribosomal RNA


Sodium dodecyl sulfate


Transcription-coupled NER


Treacle ribosome biogenesis factor 1

UBF 1/2

Upstream binding factor 1/2


Ultraviolet A, ultraviolet C



We thank Soňa Legartová for the description of FLIM-FRET methodology.

Authors’ contribution

LS was responsible for western blotting, immunofluorescence, immunoprecipitation, confocal microscopy, FLIM-FRET, and UVA irradiation. LS wrote a draft of the manuscript. DK performed the ChIP-PCR analyses and data quantifications. AK provided help with the western blotting and with the interpretation of FLIM-FRET results. EB coordinated experimental efforts, suggested experiments, finalized all images, and wrote the final version of this paper. All authors read and approved the final version of this manuscript.


This work was supported by the Czech Science Foundation (grant number: 18-07384S). Work was also supported by Strategie AV21, programme Qualitas, the Center for Epigenetics (68081707).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Institute of Biophysics of the Czech Academy of SciencesBrnoCzech Republic

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