Mitosis requires precise control of microtubule dynamics. The KinI kinesin MCAK, a microtubule depolymerase, is critical for this regulation. In a screen to discover previously uncharacterized microtubule-associated proteins, we identified ICIS, a protein that stimulates MCAK activity in vitro. Consistent with this biochemical property, blocking ICIS function in Xenopus extracts with antibodies caused excessive microtubule growth and inhibited spindle formation. Prior to anaphase, ICIS localized in an MCAK-dependent manner to inner centromeres, the chromosomal region located in between sister kinetochores. From Xenopus extracts, ICIS coimmunoprecipitated MCAK and the inner centromere proteins INCENP and Aurora B, which are thought to promote chromosome biorientation. By immunoelectron microscopy, we found that ICIS is present on the surface of inner centromeres, placing it in an ideal location to depolymerize microtubules associated laterally with inner centromeres. At inner centromeres, MCAK-ICIS may destabilize these microtubules and provide a mechanism that prevents kinetochore-microtubule attachment errors.
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http://dx.doi.org/10.1016/s1534-5807(03)00229-6 | DOI Listing |
Connections between the mechanical properties of DNA and biological functions have been speculative due to the lack of methods to measure or predict DNA mechanics at scale. Recently, a proxy for DNA mechanics, cyclizability, was measured by loop-seq and enabled genome-scale investigation of DNA mechanics. Here, we use this dataset to build a computational model predicting bias-corrected intrinsic cyclizability, with near-perfect accuracy, solely based on DNA sequence.
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March 2025
https://ror.org/0168r3w48 Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, San Diego, CA, USA
Large multiprotein machines are central to many biological processes. However, stoichiometric determination of protein complex subunits in their native states presents a significant challenge. This study addresses the limitations of current tools in accuracy and precision by introducing concatemer-assisted stoichiometry analysis (CASA).
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December 2024
Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN, USA.
Histone tail phosphorylation has diverse effects on a myriad of cellular processes, including cell division, and is highly conserved throughout eukaryotes. Histone H3 phosphorylation at threonine 3 (H3T3) during mitosis occurs at the inner centromeres and is required for proper biorientation of chromosomes on the mitotic spindle. While H3T3 is also phosphorylated during meiosis, a possible role for this modification has not been tested.
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December 2024
Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
To establish bipolar attachments of microtubules to sister chromatids, an inner kinetochore subcomplex, the constitutive centromere-associated network (CCAN), is assembled on centromeric chromatin and recruits the microtubule-binding subcomplex called the KMN network. Since CCAN proteins CENP-C and CENP-T independently bind to the Mis12 complex (Mis12C) of KMN, it is difficult to evaluate the significance of each interaction in cells. Here, we demonstrate the molecular details of the CENP-T-Mis12C interaction using chicken DT40 cells lacking the CENP-C-Mis12C interaction.
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November 2024
Department of Biochemistry, University of Washington, Seattle, United States.
Previously, we reconstituted a minimal functional kinetochore from recombinant proteins that was capable of transmitting force from dynamic microtubules to nucleosomes containing the centromere-specific histone variant Cse4 (Hamilton et al. 2020). This work revealed two paths of force transmission through the inner kinetochore: through Mif2 and through the Okp1/Ame1 complex (OA).
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