Human SAS-6 C-Terminus Nucleates and Promotes Microtubule Assembly in Vitro by Binding to Microtubules

Gupta, Hindol; Badarudeen, Binshad; George, Athira; Thomas, Geethu Emily; Gireesh, K. K.; Manna, Tapas

doi:10.1021/acs.biochem.5b00978

Cited by 10 publications

(15 citation statements)

References 35 publications

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“…The p.Met1124Val change found in this study results in the maintenance of a hydrophobic side chain, but this substitution could either prevent the PLK4-dependent phosphorylation of the surrounding residues or sterically impede the interaction between STIL and hsSAS6, in both cases resulting in the incorrect recruitment of the latter at the site of procentriole assembly. Alternatively, since hsSAS6 possesses an intrinsic microtubule assembly-promoting activity mediated by its C-terminal domain [Gupta et al, 2015], the p.Met1124Val mutation could promote hsSAS6 stabilization resulting in procentriolar microtubules over-elongation.…”

Section: Discussionmentioning

confidence: 99%

Novel STIL Compound Heterozygous Mutations Cause Severe Fetal Microcephaly and Centriolar Lengthening

Cristofoli

Keersmaecker²,

Catte³

et al. 2017

Mol Syndromol

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STIL (SCL/TAL1 interrupting locus) is a core component of the centriole duplication process. STIL mutations have been associated with both autosomal recessive primary microcephaly (MCPH) and holoprosencephaly. In this report, we describe a family with multiple miscarriages and 2 terminations of pregnancy due to marked fetal microcephaly, delayed cortical gyrification, and dysgenesis of the corpus callosum. Whole exome sequencing allowed us to identify novel compound heterozygous mutations in STIL. The mutations lie, respectively, in the CPAP/CENPJ and the hsSAS6 interacting domains of STIL. M-phase synchronized amniocytes from both affected fetuses did not display an aberrant number of centrioles, as shown previously for either STIL-depleted or overexpressing cells. However, we observed an elongation of at least 1 centriole for each duplicated centrosome. These preliminary results may point to a novel mechanism causing MCPH and embryonic lethality in humans.

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Section: Discussionmentioning

confidence: 99%

Novel STIL Compound Heterozygous Mutations Cause Severe Fetal Microcephaly and Centriolar Lengthening

Cristofoli

Keersmaecker²,

Catte³

et al. 2017

Mol Syndromol

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“…Such experiments led to the proposal that SAS‐6 ring oligomerization is at the root of cartwheel assembly . Moreover, it has been reported that the C‐terminal moiety of human HsSAS‐6 promotes microtubule assembly in vitro, raising the possibility of a direct interaction of SAS‐6 proteins and the polymer.…”

Section: Cartwheel Proteinsmentioning

confidence: 99%

The Rise of the Cartwheel: Seeding the Centriole Organelle

2018

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The cartwheel is a striking structure critical for building the centriole, a microtubule-based organelle fundamental for organizing centrosomes, cilia, and flagella. Over the last 50 years, the cartwheel has been described in many systems using electron microscopy, but the molecular nature of its constituent building blocks and their assembly mechanisms have long remained mysterious. Here, we review discoveries that led to the current understanding of cartwheel structure, assembly, and function. We focus on the key role of SAS-6 protein self-organization, both for building the signature ring-like structure with hub and spokes, as well as for their vertical stacking. The resemblance of assembly intermediates in vitro and in vivo leads us to propose a novel registration step in cartwheel biogenesis, whereby stacked SAS-6-containing rings are put in register through interactions with peripheral elements anchored to microtubules. We conclude by evoking some avenues for further uncovering cartwheel and centriole assembly mechanisms.

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“…The main component of the pro-centriole cartwheel is SAS-6, an evolutionarily conserved coiled-coil protein (9), whose. oligomerization leads to cartwheel-like assembly of the pro-centriole (18,(22)(23)(24)(25)(26)(27). SAS-6 recruitment and the cartwheel assembly begin at the G1/S entry of the cell cycle and thereafter, formation of the new centriole resumes (28)(29)(30).…”

Section: Introductionmentioning

confidence: 99%

The ubiquitin ligase FBXW7 targets the centriolar assembly protein HsSAS-6 for degradation and thereby regulates centriole duplication

Badarudeen

Gupta

Nair

et al. 2020

Journal of Biological Chemistry

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Formation of a single new centriole from a pre-existing centriole is strictly controlled to maintain correct centrosome number and spindle polarity in cells. However, the mechanisms that govern this process are incompletely understood. Here, using several human cell lines, immunofluorescence and structured illumination microscopy methods, and ubiquitination assays, we show that the E3 ubiquitin ligase F-box and WD repeat domain–containing 7 (FBXW7), a subunit of the SCF ubiquitin ligase, down-regulates spindle assembly 6 homolog (HsSAS-6), a key protein required for procentriole cartwheel assembly, and thereby regulates centriole duplication. We found that FBXW7 abrogation stabilizes HsSAS-6 and increases its recruitment to the mother centriole at multiple sites, leading to supernumerary centrioles. Ultrastructural analyses revealed that FBXW7 is broadly localized on the mother centriole and that its presence is reduced at the site where the HsSAS-6–containing procentriole is formed. This observation suggested that FBXW7 restricts procentriole assembly to a specific site to generate a single new centriole. In contrast, during HsSAS-6 overexpression, FBXW7 strongly associated with HsSAS-6 at the centriole. We also found that SCFFBXW7 interacts with HsSAS-6 and targets it for ubiquitin-mediated degradation. Further, we identified putative phosphodegron sites in HsSAS-6, whose substitutions rendered it insensitive to FBXW7-mediated degradation and control of centriole number. In summary, SCFFBXW7 targets HsSAS-6 for degradation and thereby controls centriole biogenesis by restraining HsSAS-6 recruitment to the mother centriole, a molecular mechanism that controls supernumerary centrioles/centrosomes and the maintenance of bipolar spindles.

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Human SAS-6 C-Terminus Nucleates and Promotes Microtubule Assembly in Vitro by Binding to Microtubules

Cited by 10 publications

References 35 publications

Novel STIL Compound Heterozygous Mutations Cause Severe Fetal Microcephaly and Centriolar Lengthening

Novel STIL Compound Heterozygous Mutations Cause Severe Fetal Microcephaly and Centriolar Lengthening

The Rise of the Cartwheel: Seeding the Centriole Organelle

The ubiquitin ligase FBXW7 targets the centriolar assembly protein HsSAS-6 for degradation and thereby regulates centriole duplication

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