Research: Behavior of chromosomes in bacteria and yeast We are interested in two aspects of chromosome metabolism: recombination and chromosome segregation. We analyze these processes in both prokaryotes (E. coli) and eukaryotes (yeast S. cerevisiae) using genetic, biochemical, and cytological methods. 1. Transposition in E. coli. The bacterial transposon Tn10 moves by a series of specific DNA breaking and joining events which require a Tn10-encoded transposase protein and accessory host proteins, IHF and HU. We wish to understand the precise nature andorder of reaction steps, the types of DNA/protein complexes involved, the way in which the transposon ends find one another, the mechanistic role of host factors, the importance of DNA topology, and the functional organization of transposase protein. 2. Meiosis in S. cerevisiae. During meiosis, homologous chromosomes recognize one another ("pair") and engage in recombination prior to, and as a prerequisite for, their segregation at the first meiotic division. We are examining the pairing and recombinaion processes, their control, and their integration with the cell cycle during meiosis in yeast. Genetic, cytological and biochemical approaches are used. 3. Control of replication initiation in bacteria. We are investigating the regulation of replication initiation in E. coli. We are analyzing the role of recently discovered negative regulatory protein, SeqA, which works in concert with DNA adenine methylaion at specific sites in the replication origin. We are also searching for new factors which may participate in replication timing and in maintaining coordination between initiation and cell division.
Selected Publications: Chalmers, R., Guhathakurta, A., Benjamin, H. and Kleckner, N. (1998.) IHF modulation of Tn10 transposition in vitro and in vivo: Sensory transduction of supercoiling status via a proposed protein/DNA molecular spring. Cell 93: 897-908. Kennedy, A.K., Guhathakurta, A., Kleckner, N. and Haniford, D.B. (1998.) Tn10 transposition via a DNA hairpin intermediate. Cell 95, 125-134. Burgess, S.M., Kleckner, N. and Weiner, B.M. (1999.) Somatic pairing of homologs in budding yeast: existence and modulation. Genes Dev. 13, 1627-1641. Hunter, N. and Kleckner, N. (2001.) The single-end invasion: an asymmetric intermediate at the double-strand break to double-Holliday junction transition of meiotic recombination. Cell 106: 59-70. Blat Y, Protacio RU, Hunter N, Kleckner N. (2002.) Physical and functional interactions among basic chromosome organizational features govern early steps of meiotic chiasma formation. Cell 111:791-802. Dekker, J., Rippe, K., Dekker, M. and Kleckner, N. (2002.) Capturing chromosome conformation. Science 295: 1306-1311. Cha RS, Kleckner N. (2002.) ATR homolog Mec1 promotes fork progression, thus averting breaks in replication slow zones. Science 297:602-6. Perry J, Kleckner N. (2003.) The ATRs, ATMs, and TORs are giant HEAT repeat proteins. Cell 112:151-5. Tessé, S., Storlazzi, A., Kleckner, N., Gargano, S., and Zickler, D. (2003.) Localization and roles of Ski8p in Sordaria macrospora meiosis and delineation of three mechanistically distinct steps of meiotic homolog juxtaposition. Proc. Natl. Acad. Sci, 100:12865-12870. Börner, G.V., Kleckner, N. and Hunter, N. (2004) Crossover/noncrossover differentiation, synaptonemal complex formation and regulatory surveillance at the leptotene/zygotene transition of meiosis. Cell 117, 29-45.
|
