Conservation of Epigenetic Regulation, ORC Binding and Developmental Timing of DNA Replication Origins in the Genus Drosophila

There is much interest in how DNA replication origins are regulated so that the genome is completely duplicated each cell division cycle and in how the division of cells is spatially and temporally integrated with development. In the Drosophila melanogaster ovary, the cell cycle of somatic follicle...

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Bibliographic Details
Published in:	Genetics (Austin) Vol. 177; no. 3; pp. 1291 - 1301
Main Authors:	Calvi, B.R, Byrnes, B.A, Kolpakas, A.J
Format:	Journal Article
Language:	English
Published:	United States Genetics Soc America 01-11-2007 Genetics Society of America
Subjects:	Acetylation Animals Base Sequence Binding sites Biological Evolution Cell Cycle Cell Cycle Proteins - metabolism cell division cell proliferation DNA Replication DNA-binding proteins Drosophila Drosophila - cytology Drosophila - genetics Drosophila - growth & development Drosophila - metabolism Drosophila Proteins - genetics Drosophila Proteins - metabolism embryogenesis Epigenesis, Genetic epigenetics evolution Female fruit flies Gene Amplification gene expression regulation Genetics genome insect development Kinases loci mitosis Molecular Sequence Data morphogenesis nucleosomes Nucleosomes - metabolism nucleotide sequences oogenesis Oogenesis - genetics Oogenesis - physiology Origin Recognition Complex - genetics Origin Recognition Complex - metabolism ova Ovarian Follicle - cytology Ovarian Follicle - metabolism Protein Binding Proteins Proto-Oncogene Proteins c-myb - metabolism Sequence Homology, Nucleic Acid somatic cells Special Section: 12 Drosophila Genomes Species Specificity
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Summary:	There is much interest in how DNA replication origins are regulated so that the genome is completely duplicated each cell division cycle and in how the division of cells is spatially and temporally integrated with development. In the Drosophila melanogaster ovary, the cell cycle of somatic follicle cells is modified at precise times in oogenesis. Follicle cells first proliferate via a canonical mitotic division cycle and then enter an endocycle, resulting in their polyploidization. They subsequently enter a specialized amplification phase during which only a few, select origins repeatedly initiate DNA replication, resulting in gene copy number increases at several loci important for eggshell synthesis. Here we investigate the importance of these modified cell cycles for oogenesis by determining whether they have been conserved in evolution. We find that their developmental timing has been strictly conserved among Drosophila species that have been separate for approximately 40 million years of evolution and provide evidence that additional gene loci may be amplified in some species. Further, we find that the acetylation of nucleosomes and Orc2 protein binding at active amplification origins is conserved. Conservation of DNA subsequences within amplification origins from the 12 recently sequenced Drosophila species genomes implicates members of a Myb protein complex in recruiting acetylases to the origin. Our findings suggest that conserved developmental mechanisms integrate egg chamber morphogenesis with cell cycle modifications and the epigenetic regulation of origins.
Bibliography:	http://dx.doi.org/10.1534/genetics.107.070862 Communicating editor: J. A. Birchler Corresponding author: Department of Biology, Syracuse University, 130 College Pl., BRL 703, Syracuse, NY 13244. E-mail: bcalvi@syr.edu
ISSN:	0016-6731 1943-2631 1943-2631
DOI:	10.1534/genetics.107.070862