Recognition of SUMO-modified PCNA requires tandem receptor motifs in Srs2


Ubiquitin (Ub) and ubiquitin-like (Ubl) modifiers such as SUMO (also known as Smt3 in Saccharomyces cerevisiae) mediate signal transduction through post-translational modification of substrate proteins in pathways that control differentiation, apoptosis and the cell cycle, and responses to stress such as the DNA damage response. In yeast, the proliferating cell nuclear antigen PCNA (also known as Pol30) is modified by ubiquitin in response to DNA damage and by SUMO during S phase. Whereas Ub–PCNA can signal for recruitment of translesion DNA polymerases, SUMO–PCNA signals for recruitment of the anti-recombinogenic DNA helicase Srs2. It remains unclear how receptors such as Srs2 specifically recognize substrates after conjugation to Ub and Ubls. Here we show, through structural, biochemical and functional studies, that the Srs2 carboxy-terminal domain harbours tandem receptor motifs that interact independently with PCNA and SUMO and that both motifs are required to recognize SUMO–PCNA specifically. The mechanism presented is pertinent to understanding how other receptors specifically recognize Ub- and Ubl-modified substrates to facilitate signal transduction.

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Figure 1: Srs2 C-terminal domain interacts with PCNA, SUMO and SUMO–PCNA.
Figure 2: Structures of SUMO–PCNA alone and in complex with Srs2.
Figure 3: Srs2 PIP-like motif and SIM interactions with PCNA and SUMO.
Figure 4: Srs2 PIP-like motif and SIM required for recognition of SUMO–PCNA.
Figure 5: Models for Srs2–SUMO–PCNA complexes.

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Primary accessions

Protein Data Bank

Data deposits

Atomic coordinates and structure factors are deposited in PDB under accession codes 3V60, 3V61 and 3V62.


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We thank J. Kuriyan and B. Kelch for coordinates of the T4 clamp before publication. NE-CAT beamlines (Advanced Photon Source) supported by RR-15301 (NIH NCRR). APS supported by the US Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Beamline X29 (National Synchrotron Light Source) supported by the US Department of Energy, the Office of Basic Energy Sciences and P41RR012408 (NIH NCRR). A.A.A., F.M. and C.D.L. are supported by NIH R01 GM065872 to C.D.L. and F32 GM086066 to A.A.A.

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Experiments performed and analysed by A.A.A., F.M. and C.D.L. Manuscript prepared by A.A.A and C.D.L.

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Correspondence to Christopher D. Lima.

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The authors declare no competing financial interests.

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Armstrong, A., Mohideen, F. & Lima, C. Recognition of SUMO-modified PCNA requires tandem receptor motifs in Srs2. Nature 483, 59–63 (2012).

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