Franz Klein

Meiotic chromosome segregation requires sister chromatid cohesion, initiation and completion of recombination and synapsis between homologs.

Our group is interested to understand more about the mechanisms behind these processes.

One approach is directed to the characterization of functionally important protein complexes by mass spectrometry.

In this way, we want to gain insight into protein complex formation and post transcriptional modifications, which govern their biochemical behavior.

A complementing approach deals with the characterization of in vivo protein-DNA interactions especially of proteins involved in meiotic chromosome structure and recombination.

Legend Figure 1

shows the interaction pattern of the meiotic kleisin "Rec8" with chromosomal DNA

A) by high resolution (4 nucleotide) microarray analysis and

B) by more conventional immunofluorescence labelling of spread meiotic chromosome preparations. The kleisin is a critical part of the cohesin ring, which embraces the two sister chromatids after DNA replication and helps to organize the chromosome into axis (or core) and loop regions. This functional organization can be inferred by Figure 1, B) in which anti Rec8 antibody labels chromosomal axes, from which loops protrude away. The DNA was stained by DAPI (4',6'-diamino-2-phenylindole).Chromatin immonuprecipitated with the Rec8 protein was identified by hybridization to an Affymetrics high resolution microarray covering the complete S. cerevisiae genome.Figure 1A shows peaks and valleys on a small chromosome (Chr3), where the peaks correspond to Rec8 binding sites (axis regions) and valleys to DNA loops (no Rec8, see 1B).The microarray experiments allows to determine the identity of the genome wide binding sites and allows quantification of the binding intensity. Figure 1A reveals that the region around the centromere is strongly loaded with Rec8, but that there are also other regularly spaced binding sites of intermediate strength along the chromosome arm. This leads to a model, in which the two chromatids are strongly connected at the sister centromeres, but also at regularly spaced intervals along the arms. The arm connections will be resolved during the first meiotic division, where each pair of sister centromeres is separated from its homologous pair through the release of chiasmata, while pericentromeric cohesion remains protected. It is during the second division, that this cohesion is resolved, leading to the separation of sister centromeres and thus to haploid products.

Panizza, S., Mendoza, M.A., Berlinger, M., Huang, L., Nicolas, A., Shirahige, K., and Klein, F. (2011). Spo11-accessory proteins link double-strand break sites to the chromosome axis in early meiotic recombination. Cell 146, 372-383.

Mendoza-Parra, M., A., S. Panizza and F. Klein, (2009). "Analysis of Protein-DNA Interactions During Meiosis by Quantitative Chromatin Immunoprecipitation (qChIP)." Scott Keeney (ed.), Meiosis, Volume 1, Molecular and Genetic Methods, vol. 557, Humana Press.

Penkner, A. M., Prinz, S., Ferscha, S., and Klein, F. (2005). Mnd2, an Essential Antagonist of the Anaphase-promoting Complex during Meiotic Prophase. Cell 120, 1-13.

Klein, F., Mahr, P., Galova, M., Buonomo, S.B., Michaelis, C., Nairz, K., and Nasmyth, K. (1999). A central role for cohesins in sister chromatid cohesion, formation of axial elements, and recombination during yeast meiosis. Cell 98, 91-103.