The distinct structural properties of heterochromatin accommodate a diverse group of vital chromosome functions, yet we have only rudimentary knowledge about its protein composition. One powerful tool for Drosophila biologists has been a group of genes that reverse the repressive effect of heterochromatin on the expression of a gene placed next to it ectopically. Several of these genes are known to encode proteins enriched in heterochromatin. The best characterized of these is the heterochromatin associated protein, HP1. HP1 has no known DNA-binding activity, hence its incorporation into heterochromatin is likely to be dependent upon other proteins. To examine HP1 interacting proteins, we isolated three distinct oligomeric species of HP1 from the cytoplasm of early Drosophila embryos and analyzed their compositions. The two larger oligomers resemble a fraction of that is tightly associated with the chromatin of interphase nuclei. Like the HP1 in these two cytoplasmic oligomers, this tightly bound nuclear fraction of HP1 is underphosphorylated and is associated with subunits of the origin recognition complex (ORC). We also found the localization of HP1 into heterochromatin to be disrupted in mutants for the ORC2 subunit. This phenotype supports a role for ORC in HP1 targeting and heterochromatin assembly. This proposed role for Drosophila ORC suggests striking similarities to the ability of ORC to recruit the Sir1 protein to silencing nucleation sites at the silent mating type loci in S. cerevisiae.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.20575 |
| Date | January 1998 |
| Creators | Huang, Da Wei. |
| Contributors | Kellum, Rebecca (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001610291, proquestno: MQ44185, Theses scanned by UMI/ProQuest. |
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