title: Integrative analysis of gene amplification in Drosophila follicle cells: parameters of origin activation and repression.
abstract: In metazoans, how replication origins are specified and subsequently activated is not well understood. Drosophila amplicons in follicle cells (DAFCs) are genomic regions that undergo rereplication to increase DNA copy number. We identified all DAFCs by comparative genomic hybridization, uncovering two new amplicons in addition to four known previously. The complete identification of all DAFCs enabled us to investigate these in vivo replicons with respect to parameters of transcription, localization of the origin recognition complex (ORC), and histone acetylation, yielding important insights into gene amplification as a metazoan replication model. Significantly, ORC is bound across domains spanning 10 or more kilobases at the DAFC rather than at a specific site. Additionally, ORC is bound at many regions that do not undergo amplification, and, in contrast to cell culture, these regions do not correlate with high gene expression. As a developmental strategy, gene amplification is not the predominant means of achieving high expression levels, even in cells capable of amplification. Intriguingly, we found that, in some strains, a new amplicon, DAFC-22B, does not amplify, a consequence of distant repression of ORC binding and origin activation. This repression is alleviated when a fragment containing the origin is placed in different genomic contexts.
authors: Whitehead Institute, Cambridge, Massachusetts 02142, USA.
authors: Jane C
authors: JC
authors: Kim
authors: Jared
authors: J
authors: Nordman
authors: Fang
authors: F
authors: Xie
authors: Helena
authors: H
authors: Kashevsky
authors: Thomas
authors: T
authors: Eng
authors: Sharon
authors: S
authors: Li
authors: David M
authors: DM
authors: MacAlpine
authors: Terry L
authors: TL
authors: Orr-Weaver
mesh_terms: D000107:Acetylation; D000818:Animals; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000235:genetics*; D005784:Gene Amplification; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D051738:Origin Recognition Complex / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D006657:Histones; D051738:Origin Recognition Complex