Association of the origin recognition complex with heterochromatin and HP1 in higher eukaryotes.
The origin recognition complex (ORC) is required to initiate eukaryotic DNA replication and also engages in transcriptional silencing in S. cerevisiae. We observed a striking preferential but not exclusive association of Drosophila ORC2 with heterochromatin on interphase and mitotic chromosomes. HP1, a heterochromatin-localized protein required for position effect variegation (PEV), colocalized with DmORC2 at these sites. Consistent with this localization, intact DmORC and HP1 were found in physical complex. The association was shown biochemically to require the chromodomain and shadow domains of HP1. The amino terminus of DmORC1 contained a strong HP1-binding site, mirroring an interaction found independently in Xenopus by a yeast two-hybrid screen. Finally, heterozygous DmORC2 recessive lethal mutations resulted in a suppression of PEV. These results indicate that ORC may play a widespread role in packaging chromosomal domains through interactions with heterochromatin-organizing factors.
Pak
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DT
Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
Pflumm
M
M
Chesnokov
I
I
Huang
D W
DW
Kellum
R
R
Marr
J
J
Romanowski
P
P
Botchan
M R
MR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D019976:Cloning, Organism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D006570:Heterochromatin / Q000378:metabolism*; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex; D011485:Protein Binding; D029701:Saccharomyces cerevisiae Proteins; D014981:Xenopus
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006570:Heterochromatin; C497215:ORC2 protein, S cerevisiae; C497216:Orc2 protein, Drosophila; D051738:Origin Recognition Complex; D029701:Saccharomyces cerevisiae Proteins; D000090266:Chromobox Protein Homolog 5