Cdk Activity Couples Epigenetic Centromere Inheritance to Cell Cycle Progression

Centromeres form the site of chromosome attachment to microtubules during mitosis. Identity of these loci is maintained epigenetically by nucleosomes containing the histone H3 variant CENP-A. Propagation of CENP-A chromatin is uncoupled from DNA replication initiating only during mitotic exit. We now demonstrate that inhibition of Cdk1 and Cdk2 activities is sufficient to trigger CENP-A assembly throughout the cell cycle in a manner dependent on the canonical CENP-A assembly machinery. We further show that the key CENP-A assembly factor Mis18BP1(HsKNL2) is phosphorylated in a cell cycle-dependent manner that controls its centromere localization during mitotic exit. These results strongly support a model in which the CENP-A assembly machinery is poised for activation throughout the cell cycle but kept in an inactive noncentromeric state by Cdk activity during S, G2, and M phases. Alleviation of this inhibition in G1 phase ensures tight coupling between DNA replication, cell division, and subsequent centromere maturation.FCT doctoral fellowship: (SFRH/BD/33219/2007); FCT grant: (BIA-BCM/100557/2008); Fundação Calouste Gulbenkian; European Commission FP7 programme; EMBO installation grant

Walking along chromosomes with super-resolution imaging, contact maps, and integrative modeling

Chromosome organization is crucial for genome function. Here, we present a method for visualizing chromosomal DNA at super-resolution and then integrating Hi-C data to produce three-dimensional models of chromosome organization. Using the super-resolution microscopy methods of OligoSTORM and OligoDNA-PAINT, we trace 8 megabases of human chromosome 19, visualizing structures ranging in size from a few kilobases to over a megabase. Focusing on chromosomal regions that contribute to compartments, we discover distinct structures that, in spite of considerable variability, can predict whether such regions correspond to active (A-type) or inactive (B-type) compartments. Imaging through the depths of entire nuclei, we capture pairs of homologous regions in diploid cells, obtaining evidence that maternal and paternal homologous regions can be differentially organized. Finally, using restraint-based modeling to integrate imaging and Hi-C data, we implement a method-integrative modeling of genomic regions (IMGR)-to increase the genomic resolution of our traces to 10 kb.This work was supported by funds from Ministerio de Ciencia, Innovación y Universidades of Spain (http://www.ciencia.gob.es/) (IJCI-2015-23352) to IF, Damon Runyon Cancer Research Foundation (https://www.damonrunyon.org/) and Howard Hughes Medical Institute (https://www.hhmi.org/) to BJB, Uehara Memorial Foundation Research (https://www.taisho-holdings.co.jp/en/environment/social/sciences/) to HMS, William Randolph Hearst Foundation (https://www.hearstfdn.org/) to RBM, EMBO (Long-Term fellowship) (https://www.embo.org/) to JE, NSF (Center for Theoretical Biological Physics, Rice University) (https://www.nsf.gov/) to MDP and JNO, NSF (CCF-1054898, CCF-1317291) (https://www.nsf.gov/), NIH (1R01EB018659-01, 1-U01- MH106011-01) (https://www.nih.gov/), and Office of Naval Research (N00014-13-1-0593, N00014-14-1-0610, N00014-16-1-2182, N00014-16-1- 2410) (https://www.onr.navy.mil/) to PY, NIH (1DP2OD008540, U01HL130010, UM1HG009375, 4DP2OD008540) (https://www.nih.gov/), NSF (PHY-1427654) (https://www.nsf.gov/), USDA (2017-05741) (https://www.usda.gov/), Welch Foundation (Q-1866) (http://www.welch1.org/), NVIDIA (https://www.nvidia.com/en-us/), IBM (https://www.ibm.com/us-en/?lnk=m), Google (https://www.google.com/), Cancer Prevention Research Institute of Texas (R1304) (http://www.cprit.state.tx.us/), and McNair Medical Institute (http://www.mcnairfoundation.org/what-we-fund/mcnair-medical-institute/) to E.L.A., Horizon 2020 Research and Innovation Programme (676556) (https://ec.europa.eu/programmes/horizon2020/en/), European Research Council (609989) (https://erc.europa.eu/), Ministerio de Ciencia, Innovación y Universidades of Spain (BFU2017-85926-P) (http://www.ciencia.gob.es/), CERCA, and AGAUR Programme of the Generalitat de Catalunya and Centros de Excelencia Severo Ochoa (SEV-2012-0208) (http://www.ciencia.gob.es/portal/site/MICINN/menuitem.7eeac5cd345b4f34f09dfd1001432ea0/?vgnextoid=cba733a6368c2310VgnVCM1000001d04140aRCRD) to M.A.M-R., and NIH (5DP1GM106412, R01HD091797, R01GM123289) (https://www.nih.gov/) to C-tW. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Inclusive photon production at forward rapidities in pp and p–Pb collisions at √sNN = 5.02 TeV

A study of multiplicity and pseudorapidity distributions of inclusive photons measured in pp and p−Pb collisions at a center-of-mass energy per nucleon−nucleon collision of sNN−−−√=5.02 TeV using the ALICE detector in the forward pseudorapidity region 2.3<ηlab<3.9 is presented. Measurements in p−Pb collisions are reported for two beam configurations in which the directions of the proton and lead ion beam were reversed. The pseudorapidity distributions in p−Pb collisions are obtained for seven centrality classes which are defined based on different event activity estimators, i.e., the charged-particle multiplicity measured at midrapidity as well as the energy deposited in a calorimeter at beam rapidity. The inclusive photon multiplicity distributions for both pp and p−Pb collisions are described by double negative binomial distributions. The pseudorapidity distributions of inclusive photons are compared to those of charged particles at midrapidity in \pp collisions and for different centrality classes in p−Pb collisions. The results are compared to predictions from various Monte Carlo event generators. None of the generators considered in this paper reproduces the inclusive photon multiplicity distributions in the reported multiplicity range. The pseudorapidity distributions are, however, better described by the same generators