Switch-like compaction of poly(ADP-ribose) upon cation binding

Proc Natl Acad Sci U S A. 2023 May 9;120(19):e2215068120. doi: 10.1073/pnas.2215068120. Epub 2023 May 1.

Abstract

Poly(ADP-ribose) (PAR) is a homopolymer of adenosine diphosphate ribose that is added to proteins as a posttranslational modification to regulate numerous cellular processes. PAR also serves as a scaffold for protein binding in macromolecular complexes, including biomolecular condensates. It remains unclear how PAR achieves specific molecular recognition. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) to evaluate PAR flexibility under different cation conditions. We demonstrate that, compared to RNA and DNA, PAR has a longer persistence length and undergoes a sharper transition from extended to compact states in physiologically relevant concentrations of various cations (Na+, Mg2+, Ca2+, and spermine4+). We show that the degree of PAR compaction depends on the concentration and valency of cations. Furthermore, the intrinsically disordered protein FUS also served as a macromolecular cation to compact PAR. Taken together, our study reveals the inherent stiffness of PAR molecules, which undergo switch-like compaction in response to cation binding. This study indicates that a cationic environment may drive recognition specificity of PAR.

Keywords: PAR-binding protein; persistence length; poly(ADP-ribose); single molecule FRET.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Diphosphate Ribose* / chemistry
  • Cell Physiological Phenomena
  • Poly Adenosine Diphosphate Ribose* / chemistry
  • Poly Adenosine Diphosphate Ribose* / metabolism
  • Protein Binding
  • Protein Processing, Post-Translational

Substances

  • Poly Adenosine Diphosphate Ribose
  • Adenosine Diphosphate Ribose