Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

SUMO-modified PCNA recruits Srs2 to prevent recombination during S phase


Damaged DNA, if not repaired before replication, can lead to replication fork stalling and genomic instability1,2,3; however, cells can switch to different damage bypass modes that permit replication across lesions. Two main bypasses are controlled by ubiquitin modification of proliferating cell nuclear antigen (PCNA), a homotrimeric DNA-encircling protein that functions as a polymerase processivity factor and regulator of replication-linked functions4,5. Upon DNA damage, PCNA is modified at the conserved lysine residue 164 by either mono-ubiquitin or a lysine-63-linked multi-ubiquitin chain5, which induce error-prone or error-free replication bypasses of the lesions5,6. In S phase, even in the absence of exogenous DNA damage, yeast PCNA can be alternatively modified by the small ubiquitin-related modifier protein SUMO5; however the consequences of this remain controversial5,6,7. Here we show by genetic analysis that SUMO-modified PCNA functionally cooperates with Srs2, a helicase that blocks recombinational repair by disrupting Rad51 nucleoprotein filaments8,9. Moreover, Srs2 displays a preference for interacting directly with the SUMO-modified form of PCNA, owing to a specific binding site in its carboxy-terminal tail. Our finding suggests a model in which SUMO-modified PCNA recruits Srs2 in S phase in order to prevent unwanted recombination events of replicating chromosomes.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Figure 1: Suppression of DNA damage sensitivity of RAD6 pathway mutants by deficiency in PCNA SUMOylation requires homologous recombination.
Figure 2: Srs2 preferentially binds SUMOylated PCNA.
Figure 3: Mutants deficient in PCNA SUMOylation and in the C-terminal tail of Srs2 ( srs2ΔC ) are epistatic with respect to suppression of RAD6 pathway mutants.
Figure 4: Influence of the PCNA–SUMO–Srs2 check on recombination and mutator phenotypes.


  1. Barbour, L. & Xiao, W. Regulation of alternative replication bypass pathways at stalled replication forks and its effects on genome stability: a yeast model. Mutat. Res. 532, 137–155 (2003)

    Article  CAS  Google Scholar 

  2. Smirnova, M. & Klein, H. L. Role of the error-free damage bypass postreplication repair pathway in the maintenance of genomic stability. Mutat. Res. 532, 117–135 (2003)

    Article  CAS  Google Scholar 

  3. Osborn, A. J., Elledge, S. J. & Zou, L. Checking on the fork: the DNA-replication stress-response pathway. Trends Cell Biol. 12, 509–516 (2002)

    Article  CAS  Google Scholar 

  4. Tsurimoto, T. PCNA binding proteins. Front. Biosci. 4, D849–D858 (1999)

    Article  CAS  Google Scholar 

  5. Hoege, C., Pfander, B., Moldovan, G. L., Pyrowolakis, G. & Jentsch, S. RAD6-dependent DNA repair is linked to modification of PCNA by ubiquitin and SUMO. Nature 419, 135–141 (2002)

    Article  ADS  CAS  Google Scholar 

  6. Stelter, P. & Ulrich, H. D. Control of spontaneous and damage-induced mutagenesis by SUMO and ubiquitin conjugation. Nature 425, 188–191 (2003)

    Article  ADS  CAS  Google Scholar 

  7. Haracska, L., Torres-Ramos, C. A., Johnson, R. E., Prakash, S. & Prakash, L. Opposing effects of ubiquitin conjugation and SUMO modification of PCNA on replicational bypass of DNA lesions in Saccharomyces cerevisiae . Mol. Cell. Biol. 24, 4267–4274 (2004)

    Article  CAS  Google Scholar 

  8. Veaute, X. et al. The Srs2 helicase prevents recombination by disrupting Rad51 nucleoprotein filaments. Nature 423, 309–312 (2003)

    Article  ADS  CAS  Google Scholar 

  9. Krejci, L. et al. DNA helicase Srs2 disrupts the Rad51 presynaptic filament. Nature 423, 305–309 (2003)

    Article  ADS  CAS  Google Scholar 

  10. Johnson, E. S. & Blobel, G. Cell cycle-regulated attachment of the ubiquitin-related protein SUMO to the yeast septins. J. Cell Biol. 147, 981–994 (1999)

    Article  CAS  Google Scholar 

  11. Bernier-Villamor, V., Sampson, D. A., Matunis, M. J. & Lima, C. D. Structural basis for E2-mediated SUMO conjugation revealed by a complex between ubiquitin-conjugating enzyme Ubc9 and RanGAP1. Cell 108, 345–356 (2002)

    Article  CAS  Google Scholar 

  12. Johnson, E. S. & Gupta, A. A. An E3-like factor that promotes SUMO conjugation to the yeast septins. Cell 106, 735–744 (2001)

    Article  CAS  Google Scholar 

  13. Kannouche, P. L., Wing, J. & Lehmann, A. R. Interaction of human DNA polymerase η with monoubiquitinated PCNA: a possible mechanism for the polymerase switch in response to DNA damage. Mol. Cell 14, 491–500 (2004)

    Article  CAS  Google Scholar 

  14. Watanabe, K. et al. Rad18 guides poleta to replication stalling sites through physical interaction and PCNA monoubiquitination. EMBO J. 23, 3886–3896 (2004)

    Article  CAS  Google Scholar 

  15. Symington, L. S. Role of RAD52 epistasis group genes in homologous recombination and double-strand break repair. Microbiol. Mol. Biol. Rev. 66, 630–670 (2002)

    Article  CAS  Google Scholar 

  16. Aylon, Y. & Kupiec, M. New insights into the mechanism of homologous recombination in yeast. Mutat. Res. 566, 231–248 (2004)

    Article  CAS  Google Scholar 

  17. Lawrence, C. W. & Christensen, R. B. Metabolic suppressors of trimethoprim and ultraviolet light sensitivities of Saccharomyces cerevisiae rad6 mutants. J. Bacteriol. 139, 866–887 (1979)

    CAS  PubMed  PubMed Central  Google Scholar 

  18. Aboussekhra, A. et al. RADH, a gene of Saccharomyces cerevisiae encoding a putative DNA helicase involved in DNA repair. Characteristics of radH mutants and sequence of the gene. Nucleic Acids Res. 17, 7211–7219 (1989)

    Article  CAS  Google Scholar 

  19. Schiestl, R. H., Prakash, S. & Prakash, L. The SRS2 suppressor of rad6 mutations of Saccharomyces cerevisiae acts by channeling DNA lesions into the RAD52 DNA repair pathway. Genetics 124, 817–831 (1990)

    CAS  PubMed  PubMed Central  Google Scholar 

  20. Palladino, F. & Klein, H. L. Analysis of mitotic and meiotic defects in Saccharomyces cerevisiae SRS2 DNA helicase mutants. Genetics 132, 23–37 (1992)

    CAS  PubMed  PubMed Central  Google Scholar 

  21. Ulrich, H. D. The srs2 suppressor of UV sensitivity acts specifically on the RAD5- and MMS2-dependent branch of the RAD6 pathway. Nucleic Acids Res. 29, 3487–3494 (2001)

    Article  CAS  Google Scholar 

  22. Broomfield, S. & Xiao, W. Suppression of genetic defects within the RAD6 pathway by srs2 is specific for error-free post-replication repair but not for damage-induced mutagenesis. Nucleic Acids Res. 30, 732–739 (2002)

    Article  CAS  Google Scholar 

  23. Soustelle, C. et al. A new Saccharomyces cerevisiae strain with a mutant Smt3-deconjugating Ulp1 protein is affected in DNA replication and requires Srs2 and homologous recombination for its viability. Mol. Cell. Biol. 24, 5130–5143 (2004)

    Article  CAS  Google Scholar 

  24. Uetz, P. et al. A comprehensive analysis of protein–protein interactions in Saccharomyces cerevisiae . Nature 403, 623–627 (2000)

    Article  ADS  CAS  Google Scholar 

  25. Friedl, A. A., Liefshitz, B., Steinlauf, R. & Kupiec, M. Deletion of the SRS2 gene suppresses elevated recombination and DNA damage sensitivity in rad5 and rad18 mutants of Saccharomyces cerevisiae . Mutat. Res. 486, 137–146 (2001)

    Article  CAS  Google Scholar 

  26. Aguilera, A. & Klein, H. L. Genetic control of intrachromosomal recombination in Saccharomyces cerevisiae. I. Isolation and genetic characterization of hyper-recombination mutations. Genetics 119, 779–790 (1988)

    CAS  PubMed  PubMed Central  Google Scholar 

  27. Rosche, W. A. & Foster, P. L. Determining mutation rates in bacterial populations. Methods 20, 4–17 (2000)

    Article  CAS  Google Scholar 

  28. Rong, L. & Klein, H. L. Purification and characterization of the SRS2 DNA helicase of the yeast Saccharomyces cerevisiae . J. Biol. Chem. 268, 1252–1259 (1993)

    CAS  PubMed  Google Scholar 

Download references


We thank U. Cramer for technical assistance, S. Kumar for the gift of the SRS2ΔN clone, D. Siepe for computational analysis, and E. S. Johnson, H. L. Klein, C. Pohl, H. Richly and H. D. Ulrich for materials. This work is supported (to S. J.) by the Max Planck Society, Deutsche Krebshilfe, Deutsche Forschungsgemeinschaft, and Fonds der chemischen Industrie.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Stefan Jentsch.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Methods

Additional methods and Supplementary Table 1 showing yeast strains used in this study. (PDF 59 kb)

Supplementary Figure Legends

Legends to accompany the Supplementary Figures S1-S5. (PDF 35 kb)

Supplementary Figure S1

PCNA ubiquitination is induced by DNA damage specifically in S-Phase. (PDF 79 kb)

Supplementary Figure S2

Survival rates after ultraviolet irradiation. (PDF 138 kb)

Supplementary Figure S3

PCNA SUMOylation levels are influenced by Srs2. (PDF 163 kb)

Supplementary Figure S4

Survival rates in response to ultraviolet radiation. (PDF 91 kb)

Supplementary Figure S5

The PCNA-SUMOSrs2 check operates in diploid cells. (PDF 231 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Pfander, B., Moldovan, GL., Sacher, M. et al. SUMO-modified PCNA recruits Srs2 to prevent recombination during S phase. Nature 436, 428–433 (2005).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing