Drosophila chromosome condensation proteins Topoisomerase II and Barren colocalize with Polycomb and maintain Fab-7 PRE silencing.
Mechanisms of cellular memory control the maintenance of cellular identity at the level of chromatin structure. We have investigated whether the converse is true; namely, if functions responsible for maintenance of chromosome structure play a role in epigenetic control of gene expression. We show that Topoisomerase II (TOPOII) and Barren (BARR) interact in vivo with Polycomb group (PcG) target sequences in the bithorax complex of Drosophila, including Polycomb response elements. In addition, we find that the PcG protein Polyhomeotic (PH) interacts physically with TOPOII and BARR and that BARR is required for Fab-7-regulated homeotic gene expression. Conversely, we find defects in chromosome segregation associated with ph mutations. We propose that chromatin condensation proteins are involved in mechanisms acting in interphase that regulate chromosome domain topology and are essential for the maintenance of gene expression.
Lupo
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DIBIT, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milano, Italy.
Breiling
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Bianchi
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Orlando
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D000818:Animals; D019521:Body Patterning / Q000235:genetics; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D020090:Chromosome Segregation / Q000235:genetics; D002875:Chromosomes / Q000201:enzymology*; D004250:DNA Topoisomerases, Type II / Q000032:analysis / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins; D005260:Female; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005801:Genes, Homeobox; D019476:Insect Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008938:Mitosis / Q000235:genetics; D009154:Mutation; D009698:Nucleoproteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D063150:Polycomb Repressive Complex 1; D011233:Precipitin Tests
C103227:Barr protein, Drosophila; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D009698:Nucleoproteins; C066770:Pc protein, Drosophila; C072820:ph-d protein, Drosophila; D063150:Polycomb Repressive Complex 1; D004250:DNA Topoisomerases, Type II