The next TriRhena Chromatin & Transcription Club will be held on the
30th of January 2008 at
INSTITUT DE GENETIQUE ET DE BIOLOGIE MOLECULAIRE ET
CELLULAIRE (IGBMC)
Parc d'Innovation,
1, rue Laurent Fries,
67404 ILLKIRCH Cedex,
C.U. de STRASBOURG,
France
14h-14h20
Rémi Terranova (FMI, Basel): Ezh2 directs genomic
contraction and imprinted repression in early embryos
14h20-14h40
Christine Vogler (MPI, Freiburg) The tale of a tail – Histone
H2A and the role of its C-terminal tail
14h40-15h30
Alexandre Akoulitchev (University of Oxford) Promoter
Regulation by Non-Coding RNA
15h30-15h45
Coffee break
15h45-15h50
Jonathan Frampton (ABCAM) Presentation of the new
monoclonal antibody production facility
15h50-16h10
Johan Tisserand (IGBMC, Illkirch) TIF1 is a suppressor
of
RAR oncogenicity in the liver
16h10-17h10
Nicolas Thomae (FMI) Mechanism of UV-Damage
Detection by DDB1-DDB2
17h10-18h00
Giacomo Cavalli (IGH, Montpellier) Polycomb, nuclear
organization and genome control.
Local Speakers
TIF1 is a suppressor of RAR oncogenicity in the liver
Johan Tisserand1, Konstantin Khechumian1, Marius Teletin2, Manuel Mark1,2, Benjamin
Herquel1, Florence Cammas1, Daniel Metzger1, Pierre Chambon1,2 and Régine Losson1
1
2
Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC)
Institut Clinique de la Souris (ICS)
TIF1 has been identified in a yeast genetic screen for proteins modulating the transactivation
potential of retinoic acid receptor RXR and was subsequently found to interact via a single
LxxLL motif with the AF-2 activation domain of numerous nuclear receptors, including
RARs, ERs, TRs, and VDR. TIF1 belongs to a family of chromatin transcriptional
corepressors that has emerged as key regulators of developmental and physiological
processes. To adress the physiological functions of TIF1, we have generated TIF1-null
mice by gene disruption.
We have discovered that TIF1-null mice spontaneously develop hepatocellular adenomas
and hepatocellular carcinomas. Importantly, we found that a deletion of a single RAR allele
in the TIF1-/- genetic background is capable of preventing the entire TIF1 KO-driven
oncogenic process. Taken together, these results define TIF1 as a suppressor of
tumorigenesis in the liver acting by inhibiting the oncogenic activity of RAR
Ezh2 directs genomic contraction and imprinted repression in early
embryos
Rémi Terranova 1, Shihori Yokobayashi 1, Michael B. Stadler 1, Arie P. Otte 2, Stuart H.
Orkin 3 and Antoine H.F.M Peters 1
1. Friedrich Miescher Institute for BioMedical Research, Maulbeerstrasse 66, CH-4058 Basel,
Switzerland
2. Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 406, 1098
SM Amsterdam, The Netherlands; 3. Department of Pediatrics, Division of
Hematology/Oncology, Children's Hospital, the Dana Farber, Cancer Institute, Harvard
Medical School, Boston, MA 02115, USA
In mammals, genomic imprinting regulates parental-specific expression required for normal
development. Here we characterize novel higher-order chromatin features associated with
establishing imprinted silencing at the paternal Kcnq1 cluster in early mouse embryos.
In this cluster, silencing depends on expression of the Kcnq1ot1 non-coding RNA in-cis. By
immuno-FISH, we show that proteins of Polycomb Repressive Complexes (PRC) 1 and 2,
and repressive histone modifications associate with Kcnq1ot1, and form a distinct repressive
nuclear compartment devoid of active marks and RNA polymerase II. In vivo, both PRCs
associate to Kcnq1ot1 from the zygote stage onwards, but PRC1 recruitment to Kcnq1ot1 is
PRC2-independent. Nevertheless, in the trophoblast lineage of E6.5 embryos, the PRC2
protein Ezh2 is essential for repression of paternal alleles of Kcnq1 cis-genes. Furthermore,
we observe Ezh2-dependent genomic contraction of the paternal Kcnq1 cluster, assigning a
novel role to Ezh2 in organizing large genomic clusters for gene repression.
Mechanism of UV-Damage Detection by DDB1-DDB2
Nicolas Thomae
Friedrich Miescher Institute for BioMedical Research, Maulbeerstrasse 66, CH-4058 Basel,
Switzerland
The UV-damaged DNA binding complex (UV-DDB) plays an important role in detection and
recruitment of the nucleotide excision repair (NER) machinery to sites of UV-damage in vivo.
Mutations in the DDB2 subunit result in xeroderma pigmentosum (complementation group E)
a severe UV-sensitivity syndrome with a high incidence of skin neoplasias. The DDB1
subunit directly interacts with the E3-type cullin type ligase Cul4A and Cul4B. A family of
about 40 DCAF proteins has been identified that binds to DDB1 in the presence of Cul4 and
serves as ubiquitin ligase substrate adapters. Here we present the 3.2Å crystal structure of
DDB1 bound to the damage specific adapter DDB2. DDB2 uses a helix-turn-helix motif Nterminal to a 7 bladed WD40-fold as main DDB1 binding epitope providing insight into the
architecture of a DDB1-DCAF complex. DNA binding by the complex is achieved via the
WD40 propeller of DDB2 that by itself is sufficient for DNA damage recognition. The
finding that a WD40 propeller directly binds nucleic acids has implication for a number of βpropeller proteins found associated with chromatin and nucleic acids.
The tale of a tail – Histone H2A and the role of its C-terminal tail
Christine Vogler1, Tanja Waldmann1, Pedro de Souza Rocha Simonini1, Mirek Dundr2,
Robert Schneider1
1
2
Max Planck Institut für Immunbiologie, Stübeweg 51, 79108 Freiburg
Rosalind Franklin University, 3333 Green Bay Rd., North Chicago, IL60064
In the eukaryotic nucleus the DNA is organized in the form of chromatin. The basic unit of
chromatin is the nucleosome consisting of 146 bp of DNA wrapped around an octamer of the
four core histones H2A, H2B, H3 and H4. The histone proteins are not only important for the
compaction of chromatin but also play an important role in the regulation of DNA-dependent
processes such as transcription and repair. Posttranslational modifications of the flexible tails
of the histones are one way to achieve this regulation. H2A is the only core histone that not
only has an N-terminal tail but additionally contains a flexible C-terminal tail. This tail is
thought to be located at the entry and exit site of the nucleosomal DNA. Almost nothing is
known about the role of this tail in chromatin structure and function nor about proteins
interacting with it. We were able to show that this tail is important for nucleosome stability in
vitro and in vivo and that its deletion significantly increases nucleosome mobility.
Furthermore, we found that expression of C-terminally truncated H2A influences cell
proliferation and cell cycle progression in vivo. This is the first demonstration of a biological
function for the H2A C-terminus.
Invited Speakers
Promoter Regulation by Non-Coding RNA
Alexandre Akoulitchev
Oxford BioDynamics Limited
Oxford University Begbroke Science Park
Sandy Lane, Yarnton
Oxford OX5 1PF
Sir William Dunn School of Pathology,
University of Oxford
Oxford OX1 3RE
The complex population of human, regulatory non-coding RNAs includes transcripts
implicated in highly specific regulation of gene promoters. One of the examples is the cellcycle dependent DHFR gene. The specificity and efficiency of its regulation depends on a
number of epigenetic mechanisms, which include high-order chromatin structures, RNAdependent interactions and promoter-specific interference.
Multiple evidence points at a mechanism of DHFR promoter repression in which a noncoding RNA initiates a cascade of epigenetic events similar to transcriptional gene silencing.
Polycomb, nuclear organization and genome control.
Giacomo Cavalli
Institute of Human Genetics, CNRS, 141, rue de la Cardonille, 34396 Montpellier Cedex 5,
France.
Polycomb and trithorax group (PcG and trxG) proteins maintain the memory of regulatory
states of developmental genes via modulation of higher-order chromatin structure. In
Drosophila, PcG complexes are recruited to specific DNA regions called PcG response
elements (PREs) ). DNA binding proteins bind to these specific sequences, and recruit the
PcG complex PRC2, which is capable of trimethylating lysine 27 of histone H3. This in turns
recruit the PRC1 complex that can somehow elicit gene silencing. However, the "code" that
allows recruitment of PRC2 and PRC1 proteins at PREs is largely unknown, and we are
trying to understand it by systematic mapping genomic binding of the putative recruiter
factors.
PcG proteins bound to chromatin are not homogeneously distributed in the cell nucleus, but
they form nuclear compartments called “PcG bodies”. We are trying to understand the role of
PcG bodies in gene regulation and, more generally, the role of PcG proteins in the regulation
of cell differentiation versus proliferation during development.