Cryo-EM structure of the human CST-Polα/primase complex in a recruitment state

Nat Struct Mol Biol. 2022 Aug;29(8):813-819. doi: 10.1038/s41594-022-00766-y. Epub 2022 May 16.


The CST-Polα/primase complex is essential for telomere maintenance and functions to counteract resection at double-strand breaks. We report a 4.6-Å resolution cryo-EM structure of human CST-Polα/primase, captured prior to catalysis in a recruitment state stabilized by chemical cross-linking. Our structure reveals an evolutionarily conserved interaction between the C-terminal domain of the catalytic POLA1 subunit and an N-terminal expansion in metazoan CTC1. Cross-linking mass spectrometry and negative-stain EM analysis provide insight into CST binding by the flexible POLA1 N-terminus. Finally, Coats plus syndrome disease mutations previously characterized to disrupt formation of the CST-Polα/primase complex map to protein-protein interfaces observed in the recruitment state. Together, our results shed light on the architecture and stoichiometry of the metazoan fill-in machinery.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cryoelectron Microscopy
  • DNA Primase* / genetics
  • DNA Primase* / metabolism
  • Humans
  • Shelterin Complex
  • Telomere / metabolism
  • Telomere-Binding Proteins* / metabolism


  • Shelterin Complex
  • Telomere-Binding Proteins
  • DNA Primase