Professor
RutgersUniversity
Dept. Molecular Biology & Biochemistry
Nelson Biological Labs. Room A121
Piscataway. NJ 08854
(732) 445-2446
FAX - 2447
Chromatin structure and dynamics. polycomb silencing mechanisms. epigenetic mechanisms. developmental gene regulation. genomic programming. Drosophila genetics
The DNA sequence encodes genetic information but additional and very important layers of information are stored in the way the genetic material is organized. arranged and utilized in the nucleus. In eukaryotes. the first layer of organization is provided by the core histones around which the DNA wraps to form nucleosomes. The nucleosomes not only package the DNA but also associate with the packet a large amount of information. stored in a range of covalent modifications of the core histones. The modifications reflect the recent functional history of the particular genomic segment and influence its local availability. its structural and transcriptional properties and its interactions with the architecture of the nucleus.
We study Polycomb mechanisms. one of the major chromatin managing mechanisms in higher eukaryotes. First discovered in Drosophila as regulators of homeotic genes. they are now known to be important also in mammals for a range of phenomena from X chromosome inactivation to the regulation of cell proliferation. the maintenance of various kinds of stem cells. gene silencing. genome programming and at least some kinds of genetic imprinting. Polycomb complexes can establish and epigenetically maintain a silenced state of a chromatin domain such that the genes in that domain become transcriptionally incompetent. An alternative epigenetic mark established by a complex involving the Trithorax protein can protect genes from Polycomb silencing. The epigenetic status of a chromatin domain can be transmitted through mitosis to daughter cells and. in some cases. transmission occurs also through meiosis and inherited by the progeny of the organism.
The epigenetic marks associated with Polycomb silencing are histone deacetylation. histone H3 trimethylation at lysine 9 and lysine 27. histone H2A ubiquitylation. We do not yet understand all the roles of these modifications. although we know that the H3 methylation is read by the Polycomb chromodomain and increases the affinity of Polycomb for nucleosomes. These marks serve as a kind of memory of which chromatin domains were silenced in the previous cell cycle and should be silenced again.
In our current work. we are trying to analyse the mechanisms of recruitment of Polycomb complexes. how the component proteins interact with one another. with nucleosomes and with the transcriptional machinery. We are studying the nature of the epigenetic marks. the effects on promoters and on transcription and the interactions between Polycomb complexes and other chromatin structures such as insulators. boundary elements. telomeres. heterochromatin. We are also interested in the way in which these interactions contribute to the nuclear architecture and in the consequences for genomic programming. gene expression and cell fate.
Selected Publications
Schwartz YB, Pirrotta V. (2008) Polycomb complexes and epigenetic states. Curr Opin Cell Biol. 20(3):266-73.
Sarma K, Margueron R, Ivanov A, Pirrotta V, Reinberg D. (2008) Ezh2 requires PHF1 to efficiently catalyze H3 lysine 27 trimethylation in vivo. Mol Cell Biol. 28(8):2718-31.
Ohno K, McCabe D, Czermin B, Imhof A, Pirrotta V. (2008) ESC, ESCL and their roles in Polycomb Group mechanisms. Mech Dev. 125(5-6):527-41.
Gohl D, Müller M, Pirrotta V, Affolter M, Schedl P. (2008) Enhancer blocking and transvection at the Drosophila apterous locus. Genetics. 178(1):127-43.
Misulovin Z, Schwartz YB, Li XY, Kahn TG, Gause M, MacArthur S, Fay JC, Eisen MB, Pirrotta V, Biggin MD, Dorsett D. (2008) Association of cohesin and Nipped-B with transcriptionally active regions of the Drosophila melanogaster genome. Chromosoma. 117(1):89-102.
Konev AY, Tribus M, Park SY, Podhraski V, Lim CY, Emelyanov AV, Vershilova E, Pirrotta V, Kadonaga JT, Lusser A, Fyodorov DV. (2007) CHD1 motor protein is required for deposition of histone variant H3.3 into chromatin in vivo. Science. 317(5841):1087-90.
Schwartz YB, Pirrotta V. (2007) Polycomb silencing mechanisms and the management of genomic programmes. Nat Rev Genet. 8(1):9-22. Review.
Golovnin A, Mazur A, Kopantseva M, Kurshakova M, Gulak PV, Gilmore B, Whitfield WG, Geyer P, Pirrotta V, Georgiev P. (2007) Integrity of the Mod(mdg4)-67.2 BTB domain is critical to insulator function in Drosophila melanogaster. Mol Cell Biol. 27(3):963-74.
Pirrotta V, van Lohuizen M. (2006) Differentiation and gene regulation. Genomic programs and differentiation: editorial overview. Curr Opin Genet Dev. 16(5):443-6.
Kahn TG, Schwartz YB, Dellino GI, Pirrotta V. (2006) Polycomb complexes and the propagation of the methylation mark at the Drosophila ubx gene. J Biol Chem. 281(39):29064-75.
Schwartz YB. Kahn TG. Nix DA. Li XY. Bourgon R. Biggin M. Pirrotta V. (2006) Genome-wide analysis of Polycomb targets in Drosophila melanogaster. Nat Genet. 38(6):700-5.
Vazquez J. Muller M. Pirrotta V. Sedat JW. (2006) The Mcp element mediates stable long-range chromosome-chromosome interactions in Drosophila. Mol Biol Cell. 17(5):2158-65.
Pirrotta V. Gross DS. (2005) Epigenetic silencing mechanisms in budding yeast and fruit fly: different paths. same destinations. Mol Cell. 18(4):395-8.
Schwartz. Y.B.. Kahn. T.G. and Pirrotta. V. (2005) Characteristic low density and shear sensitivity of crosslinked chromatin containing Polycomb complexes. Mol. Cell. Biol. 25:432-439.
Dellino. G.I.. Schwartz. Y.B.. Farkas. G. McCabe. D.. Elgin. S.C.R. and Pirrotta. V. (2004) Polycomb silencing blocks transcription initiation. Mol. Cell 13:887-893.
Czermin. B.. Melfi. R. McCabe. D.. Seitz. V.. Imhof. A. and Pirrotta. V. (2002) Drosophila Enhancer of zeste/ESC complexes have a histone H3 methyltransferase activity that marks chromosomal Polycomb sites. Cell 111: 185-196.
Poux. S.. Horard. B.. Sigrist. C.J.A. and Pirrotta. V. (2002) The Drosophila Trithorax protein is a coactivator required to prevent re-establishment of Polycomb silencing. Development 129:2483-2493.
Poux. S.. Melfi. R. and Pirrotta. V. (2001) Establishment of Polycomb silencing requires a transient interaction between PC and ESC. Genes Dev. 15: 2509-2514.
Poux. S.. McCabe. D. and Pirrotta. V. (2001) Recruitment of components of Polycomb Group chromatin complexes in Drosophila. Development 128:75-85.
Muravyova. E.. A. Golovnin. E. Gracheva. A. Parshikov. T. Belenkaya. V. Pirrotta. P. Georgiev (2001) Loss of insulator activity by paired su(Hw) chromatin insulators. Science. 291:495-498.
Larsson. J.. Chen. J.D.. Rasheva. V.. Rasmuson-Lestander. Å. and Pirrotta. V. (2001) Painting of Fourth. a novel chromosome-specific protein in Drosophila. Proc. Natl. Acad. Sci. USA 98:6273-6278.
Horard. B.. Tatout. C.. Poux. S. and Pirrotta. V. (2000) Structure of a Polycomb Response Element and in vitro binding of PcG complexes containing GAGA factor. Mol. Cell Biol. 20:3187-3197.