Details

Autor(en) / Beteiligte

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

Titel

Macromolecular Assemblies of the Mammalian Circadian Clock

Ist Teil von

• Molecular cell, 2017-09, Vol.67 (5), p.770-782.e6

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2017

Link zum Volltext

Quelle

ScienceDirect

Beschreibungen/Notizen

• 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. [Display omitted] •Macromolecular organization of the core circadian clock proteins in the cell•Evidence for a cytoplasmic assembly pathway for circadian clock PERIOD complexes•Electron microscopy images of nuclear and cytoplasmic PERIOD complexes Aryal et al. report that core circadian clock proteins in the nucleus are present together in an ∼1.9-MDa, quasi-spherical, 40-nm complex. In the cytoplasm, clock proteins are incorporated into several complexes of ∼0.9–1.1 MDa, representing a likely assembly pathway. Two are flexible, multi-globular structures of ∼20 and ∼25 nm, respectively.