Biology subjects

Potocnjak, M.

Publications and source records attributed to Potocnjak, M..

3 recordsLinked to original sources

bioRxiv2022

Quantitative crosslinking and mass spectrometry determine binding interfaces and affinities mediating kinetochore stabilization

Crosslinking and mass spectrometry (XLMS) are used in integrative structural biology to acquire spatial restraints. We found a dependency between crosslink distances and intensities and developed a quantitative workflow to simultaneously estimate apparent dissociation constants (KD) of contacts within multi-subunit complexes and to aid interface prediction. Quantitative XLMS was applied to study the assembly of the macromolecular kinetochore complex, which is built on centromeric chromatin and establishes a stable link to spindle microtubules in order to segregate chromosomes during cell division. Inter-protein crosslink intensities facilitated determination of phosphorylation-induced binding interfaces and affinity changes. Phosphorylation of outer and inner kinetochore proteins mediated cooperative kinetochore stabilization and decreased the KD values of its interactions to the centromeric nucleosome by ~200-fold, which was essential for cell viability. This work demonstrates the potential of quantitative XLMS for characterizing mechanistic effects on protein assemblies upon post-translational modifications or cofactor interaction and for biological modeling.

biochemistry↗

bioRxiv2021

Microtubule plus-end regulation by centriolar cap proteins

Centrioles are microtubule-based organelles required for the formation of centrosomes and cilia. Centriolar microtubules, unlike their cytosolic counterparts, grow very slowly and are very stable. The complex of centriolar proteins CP110 and CEP97 forms a cap that stabilizes the distal centriole end and prevents its over-elongation. Here, we used in vitro reconstitution assays to show that whereas CEP97 does not interact with microtubules directly, CP110 specifically binds microtubule plus ends, potently blocks their growth and induces microtubule pausing. Cryo-electron tomography indicated that CP110 binds to the luminal side of microtubule plus ends and reduces protofilament peeling. Furthermore, CP110 directly interacts with another centriole biogenesis factor, CPAP/SAS- 4, which tracks growing microtubule plus ends, slows down their growth and prevents catastrophes. CP110 and CPAP synergize in inhibiting plus-end growth, and this synergy depends on their direct binding. Together, our data reveal a molecular mechanism controlling centriolar microtubule plus- end dynamics and centriole biogenesis.

cell biology↗

bioRxiv2018

The COMA complex is required for positioning Ipl1 activity proximal to Cse4 nucleosomes in budding yeast

Kinetochores are macromolecular protein complexes assembled on centromeric chromatin that ensure accurate chromosome segregation by linking DNA to spindle microtubules and integrating safeguard mechanisms. A kinetochore-associated pool of Ipl1Aurora B kinase, a subunit of the chromosomal passenger complex (CPC), was previously implicated in feedback control mechanisms. To study the kinetochore subunit connectivity built on budding yeast point centromeres and its CPC interactions we performed crosslink-guided in vitro reconstitution. The Ame1/Okp1CENP-U/Q heterodimer, forming the COMA complex with Ctf19/Mcm21CENP-P/O, selectively bound Cse4CENP-A nucleosomes through the Cse4 N-terminus and thereby establishes a direct link to the outer kinetochore MTW1 complex. The Sli15/Ipl1INCENP/Aurora B core-CPC interacted with COMA through the Ctf19 C-terminus, and artificial tethering of Sli15 to Ame1/Okp1 rescued synthetic lethality upon Ctf19/Mcm21 deletion in a Sli15 centromere-targeting deficient mutant. This study reveals characteristics of the inner kinetochore architecture assembled at point centromeres and the relevance of its Sli15/Ipl1 interaction for CPC function.

cell biology↗