PT  - JOURNAL ARTICLE
AU  - Marina Feric
AU  - Tyler G. Demarest
AU  - Jane Tian
AU  - Deborah L. Croteau
AU  - Vilhelm A. Bohr
AU  - Tom Misteli
TI  - Self-assembly of multi-component mitochondrial nucleoids via phase separation
AID  - 10.1101/822858
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 822858
4099  - http://biorxiv.org/content/early/2020/07/20/822858.short
4100  - http://biorxiv.org/content/early/2020/07/20/822858.full
AB  - Mitochondria contain an autonomous and spatially segregated genome. The organizational unit of their genome is the nucleoid, which consists of mitochondrial DNA (mtDNA) and associated architectural proteins. Here, we show that phase separation is the primary physical mechanism for assembly and size-control of the mitochondrial nucleoid. The major mtDNA-binding protein TFAM spontaneously phase separates in vitro via weak, multivalent interactions into viscoelastic droplets with slow internal dynamics. In combination, TFAM and mtDNA form multiphase, gel-like structures in vitro, which recapitulate the in vivo dynamic behavior of mt-nucleoids. Enlarged, phase-separated, yet transcriptionally active, nucleoids are present in mitochondria from patients with the premature aging disorder Hutchinson-Gilford Progeria Syndrome (HGPS) and are associated with mitochondrial dysfunction. These results point to phase separation as an evolutionarily conserved mechanism of genome organization.HighlightsMitochondrial genomes are organized by phase separation.The main packaging protein TFAM and mtDNA combine to form viscoelastic, multiphase droplets in vitro.Mitochondrial nucleoids exhibit phase behavior in vivo, including dynamic rearrangements and heterogenous organization.Coalescence and enlargement of mt-nucleoids occur upon loss of mitochondrial homeostasis as well as in prematurely aged cells and are associated with mitochondrial dysfunction.Competing Interest StatementThe authors have declared no competing interest.