KDM2B variants in the CxxC domain impair its DNA-binding ability and cause a distinct neurodevelopmental syndrome.

Rare variants affecting the epigenetic regulator KDM2B cause a recently delineated neurodevelopmental disorder. Interestingly, we previously identified both a general KDM2B-associated episignature and a subsignature specific to variants in the DNA-binding CxxC domain. In light of the existence of a distinct subsignature, we set out to determine if KDM2B CxxC variants are associated with a unique phenotype and disease mechanism.

Delineation of a KDM2B-related neurodevelopmental disorder and its associated DNA methylation signature.

Purpose: Pathogenic variants in genes involved in the epigenetic machinery are an emerging cause of neurodevelopment disorders (NDDs). Lysine-demethylase 2B (KDM2B) encodes an epigenetic regulator and mouse models suggest an important role during development. We set out to determine whether KDM2B variants are associated with NDD.

Mechanistic basis for Sgo1-mediated centromere localization and function of the CPC.

Centromere association of the chromosomal passenger complex (CPC; Borealin-Survivin-INCENP-Aurora B) and Sgo1 is crucial for chromosome biorientation, a process essential for error-free chromosome segregation. Phosphorylated histone H3 Thr3 (H3T3ph; directly recognized by Survivin) and histone H2A Thr120 (H2AT120ph; indirectly recognized via Sgo1), together with CPC's intrinsic nucleosome-binding ability, facilitate CPC centromere recruitment. However, the molecular basis for CPC-Sgo1 binding and how their physical interaction influences CPC centromere localization are lacking.

Leave no sister behind.

Recent work published in Cell Reports and Developmental Cell from Sen et al., Orr et al., and Papini et al.

Changing places: Chromosomal Passenger Complex relocation in early anaphase.

The Chromosomal Passenger Complex (CPC) regulates a plethora of processes during multiple stages of nuclear and cytoplasmic division. Early during mitosis, the CPC is recruited to centromeres and kinetochores, and ensures that the duplicated chromosomes become properly connected to microtubules from opposite poles of the mitotic spindle. Progression into anaphase is accompanied by a striking relocation of the CPC from centromeres to the antiparallel microtubule overlaps of the anaphase spindle and to the equatorial cortex.

Delaying the final cut: A close encounter of checkpoint kinases at the midbody.

How chromatin bridges are relayed to the chromosomal passenger complex (CPC) during mammalian cell division is unknown. In this issue, Petsalaki and Zachos (2020. J.

Untangling the contribution of Haspin and Bub1 to Aurora B function during mitosis.

Aurora B kinase is essential for faithful chromosome segregation during mitosis. During (pro)metaphase, Aurora B is concentrated at the inner centromere by the kinases Haspin and Bub1. However, how Haspin and Bub1 collaborate to control Aurora B activity at centromeres remains unclear.

The Ins and Outs of Aurora B Inner Centromere Localization.

Error-free chromosome segregation is essential for the maintenance of genomic integrity during cell division. Aurora B, the enzymatic subunit of the Chromosomal Passenger Complex (CPC), plays a crucial role in this process. In early mitosis Aurora B localizes predominantly to the inner centromere, a specialized region of chromatin that lies at the crossroads between the inter-kinetochore and inter-sister chromatid axes.

Baculoviral delivery of CRISPR/Cas9 facilitates efficient genome editing in human cells.

The CRISPR/Cas9 system is a highly effective tool for genome editing. Key to robust genome editing is the efficient delivery of the CRISPR/Cas9 machinery. Viral delivery systems are efficient vehicles for the transduction of foreign genes but commonly used viral vectors suffer from a limited capacity in the genetic information they can carry.

Inner centromere localization of the CPC maintains centromere cohesion and allows mitotic checkpoint silencing.

Faithful chromosome segregation during mitosis requires that the kinetochores of all sister chromatids become stably connected to microtubules derived from opposite spindle poles. How stable chromosome bi-orientation is accomplished and coordinated with anaphase onset remains incompletely understood. Here we show that stable chromosome bi-orientation requires inner centromere localization of the non-enzymatic subunits of the chromosomal passenger complex (CPC) to maintain centromeric cohesion.

Inter-domain Cooperation in INCENP Promotes Aurora B Relocation from Centromeres to Microtubules.

The chromosomal passenger complex is essential for error-free chromosome segregation and proper execution of cytokinesis. To coordinate nuclear division with cytoplasmic division, its enzymatic subunit, Aurora B, relocalizes from centromeres in metaphase to the spindle midzone in anaphase. In budding yeast, this requires dephosphorylation of the microtubule-binding (MTB) domain of the INCENP analog Sli15.

Sequential multisite phospho-regulation of KNL1-BUB3 interfaces at mitotic kinetochores.

Regulated recruitment of the kinase-adaptor complex BUB1/BUB3 to kinetochores is crucial for correcting faulty chromosome-spindle attachments and for spindle assembly checkpoint (SAC) signaling. BUB1/BUB3 localizes to kinetochores by binding phosphorylated MELT motifs (MELpT) in the kinetochore scaffold KNL1. Human KNL1 has 19 repeats that contain a MELT-like sequence.

Detailed imaging and genetic analysis reveal a secondary BRAF(L505H) resistance mutation and extensive intrapatient heterogeneity in metastatic BRAF mutant melanoma patients treated with vemurafenib.

Resistance to treatment is the main problem of targeted treatment for cancer. We followed ten patients during treatment with vemurafenib, by three-dimensional imaging. In all patients, only a subset of lesions progressed.

ESCRT-III binding protein MITD1 is involved in cytokinesis and has an unanticipated PLD fold that binds membranes.

The endosomal sorting complexes required for transport (ESCRT) proteins have a critical function in abscission, the final separation of the daughter cells during cytokinesis. Here, we describe the structure and function of a previously uncharacterized ESCRT-III interacting protein, MIT-domain containing protein 1 (MITD1). Crystal structures of MITD1 reveal a dimer, with a microtubule-interacting and trafficking (MIT) domain at the N terminus and a unique, unanticipated phospholipase D-like (PLD) domain at the C terminus that binds membranes.

Assembly and regulation of the membrane attack complex based on structures of C5b6 and sC5b9.

Activation of the complement system results in formation of membrane attack complexes (MACs), pores that disrupt lipid bilayers and lyse bacteria and other pathogens. Here, we present the crystal structure of the first assembly intermediate, C5b6, together with a cryo-electron microscopy reconstruction of a soluble, regulated form of the pore, sC5b9. Cleavage of C5 to C5b results in marked conformational changes, distinct from those observed in the homologous C3-to-C3b transition.

Kinases charging to the membrane.

Being at the right place and time is as fundamental to biology as it is to academic careers. In this issue, Moravcevic and colleagues (2010) survey membrane-interacting proteins in yeast and discover a new membrane-targeting module, the kinase associated-1 domain KA1, which ensures that proteins are active at the correct place and time.

Fifteen novel mutations in PKLR associated with pyruvate kinase (PK) deficiency: structural implications of amino acid substitutions in PK.

Pyruvate kinase (PK) deficiency is a rare disease but an important cause of hereditary nonspherocytic hemolytic anemia. The disease is caused by mutations in the PKLR gene and shows a marked variability in clinical expression. We report on the molecular characterization of 38 PK-deficient patients from 35 unrelated families.

Structure of Epac2 in complex with a cyclic AMP analogue and RAP1B.

Epac proteins are activated by binding of the second messenger cAMP and then act as guanine nucleotide exchange factors for Rap proteins. The Epac proteins are involved in the regulation of cell adhesion and insulin secretion. Here we have determined the structure of Epac2 in complex with a cAMP analogue (Sp-cAMPS) and RAP1B by X-ray crystallography and single particle electron microscopy.

Structure of C8alpha-MACPF reveals mechanism of membrane attack in complement immune defense.

Membrane attack is important for mammalian immune defense against invading microorganisms and infected host cells. Proteins of the complement membrane attack complex (MAC) and the protein perforin share a common MACPF domain that is responsible for membrane insertion and pore formation. We determined the crystal structure of the MACPF domain of complement component C8alpha at 2.

Paratope determination of the antithrombotic antibody 82D6A3 based on the crystal structure of its complex with the von Willebrand factor A3-domain.

The antithrombotic monoclonal antibody 82D6A3 is directed against amino acids Arg-963, Pro-981, Asp-1009, Arg-1016, Ser-1020, Met-1022, and His-1023 of the von Willebrand factor A3-domain (Vanhoorelbeke, K., Depraetere, H., Romijn, R.