Macromolecular Assemblies of the Mammalian Circadian Clock

Rajindra P. Aryal, Pieter Bas Kwak, Alfred G. Tamayo, Michael Gebert, Po-Lin Chiu, Thomas Walz, Charles J. Weitz

Research output: Contribution to journalArticlepeer-review

155 Scopus citations


The mammalian circadian clock is built on a feedback loop in which PER and CRY proteins repress their own transcription. We found that in mouse liver nuclei all three PERs, both CRYs, and Casein Kinase-1δ (CK1δ) are present together in an ∼1.9-MDa repressor assembly that quantitatively incorporates its CLOCK-BMAL1 transcription factor target. Prior to incorporation, CLOCK-BMAL1 exists in an ∼750-kDa complex. Single-particle electron microscopy (EM) revealed nuclear PER complexes purified from mouse liver to be quasi-spherical ∼40-nm structures. In the cytoplasm, PERs, CRYs, and CK1δ were distributed into several complexes of ∼0.9–1.1 MDa that appear to constitute an assembly pathway regulated by GAPVD1, a cytoplasmic trafficking factor. Single-particle EM of two purified cytoplasmic PER complexes revealed ∼20-nm and ∼25-nm structures, respectively, characterized by flexibly tethered globular domains. Our results define the macromolecular assemblies comprising the circadian feedback loop and provide an initial structural view of endogenous eukaryotic clock machinery.

Original languageEnglish (US)
Pages (from-to)770-782.e6
JournalMolecular Cell
Issue number5
StatePublished - Sep 7 2017

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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