dictyNews Electronic Edition Volume 43, number 1 January 13, 2017 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase HAPPY NEW YEAR! ========= Abstracts ========= Early nucleolar disorganization in Dictyostelium cell death MF Luciani, Y Song, A Sahrane, A Kosta, P Golstein Cell Death and Disease, in press Cell death occurs in all eukaryotes, but it is still not known whether some core steps of the cell death process are conserved. We investigated this using the protist Dictyostelium. The dissection of events in Dictyostelium vacuolar developmental cell death was facilitated by the sequential requirement for two distinct exogenous signals. An initial exogenous signal (starvation and cAMP) recruited most cells into clumps. Only within these clumps did subsequent cell death events take place. Contrary to our expectations, already this initial signal provoked nucleolar disorganization and irreversible inhibition of rRNA and DNA synthesis, reflecting marked cell dysfunction. The initial signal also primed clumped cells to respond to a second exogenous signal (DIF-1 or c-di-GMP), which led to vacuolization and synthesis of cellulose encasings. Thus, the latter prominent hallmarks of developmental cell death were induced separately from initial cell dysfunction. We propose that (1) in Dictyostelium vacuolization and cellulose encasings are late, organism-specific, hallmarks, and (2) on the basis of our observations in this protist and of similar previous observations in some cases of mammalian cell death, early inhibition of rRNA synthesis and nucleolar disorganization may be conserved in some eukaryotes to usher in developmental cell death. submitted by: Pierre Golstein [golstein@ciml.univ-mrs.fr] ——————————————————————————————————————— CP39, CP75 and CP91 are major structural components of the Dictyostelium centrosome's core structure Irene Meyer, Tatjana Peter, Petros Batsios, Oliver Kuhnert, Anne Krüger-Genge, Carl Camurça, Ralph Gräf University of Potsdam Eur. J. Cell Biol., in press The acentriolar Dictyostelium centrosome is a nucleus-associated body consisting of a core structure with three plaque-like layers, which are surrounded by a microtubule-nucleating corona. The core duplicates once per cell cycle at the G2/M transition, whereby its central layer disappears and the two outer layers form the mitotic spindle poles. Through proteomic analysis of isolated centrosomes we have identified CP39 and CP75, two essential components of the core structure. Both proteins can be assigned to the central core layer as their centrosomal presence is correlated to the disappearance and reappearance of the central core layer in the course of centrosome duplication. Both proteins contain centrosomal targeting domains in their N- and C-terminal halves whereby the N-terminal half is required for cell cycle-dependent regulation. CP39 is capable of self-interaction and overexpression of GFP- CP39 elicits supernumerary microtubule- organizing centers and precentrosomal cytosolic clusters. Underexpression stops cell growth and reverses the MTOC amplification phenotype. Depletion of CP75 by RNAi also elicits supernumerary MTOCs. In addition CP75RNAi affects correct chromosome segregation and causes co-depletion of CP39 and CP91, another central core layer component. CP39 and CP75 interact with each other directly in a yeast two hybrid assay. Furthermore CP39, CP75 and CP91 mutually interact in a proximity-dependent biotin identification (BioID) assay. Our data indicate that these three proteins are all required for proper centrosome biogenesis and make up the major structural components of core structure's central layer. submitted by: Ralf Gräf [rgraef@uni-potsdam.de] ============================================================== [End dictyNews, volume 43, number 1]