In vivo analysis of <Emphasis Type="Italic">Drosophila</Emphasis> SU(<Emphasis Type="Italic">Z</Emphasis>)12 function |
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Authors: | Sa Chen Anna Birve Åsa Rasmuson-Lestander |
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Institution: | 1.Department of Molecular Biology,Ume? University,Ume?,Sweden |
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Abstract: | Polycomb group (PcG) proteins are required to maintain a stable repression of the homeotic genes during Drosophila development. Mutants in the PcG gene Supressor of zeste 12 (Su(z)12) exhibit strong homeotic transformations caused by widespread misexpression of several homeotic genes in embryos and larvae.
Su(z)12 has also been suggested to be involved in position effect variegation and in regulation of the white gene expression in combination with zeste. To elucidate whether SU(Z)12 has any such direct functions we investigated the binding pattern to polytene chromosomes and
compared the localization to other proteins. We found that SU(Z)12 binds to about 90 specific eukaryotic sites, however, not
the white locus. We also find staining at the chromocenter and the nucleolus. The binding along chromosome arms is mostly in interbands
and these sites correlate precisely with those of Enhancer-of-zeste and other components of the PRC2 silencing complex. This
implies that SU(Z)12 mainly exists in complex with PRC2. Comparisons with other PcG protein-binding patterns reveal extensive
overlap. However, SU(Z)12 binding sites and histone 3 trimethylated lysine 27 residues (3meK27 H3) do not correlate that well.
Still, we show that Su(z)12 is essential for tri-methylation of the lysine 27 residue of histone H3 in vivo, and that overexpression of SU(Z)12 in somatic
clones results in higher levels of histone methylation, indicating that SU(Z)12 is rate limiting for the enzymatic activity
of PRC2. In addition, we analyzed the binding pattern of Heterochromatin Protein 1 (HP1) and found that SU(Z)12 and HP1 do
not co-localize. |
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Keywords: | Drosophila melanogaster Suppressor of zeste 12 Polytene chromosome binding Histone 3 methylation |
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