Affiliation:
1. Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington
Abstract
ABSTRACT
Human matrix attachment regions (MARs) can insulate transgene expression from chromosomal position effects in
Drosophila melanogaster
. To gain insight into the mechanism(s) by which chromosomal insulation occurs, we studied the expression phenotypes of
Drosophila
transformants expressing mini-
white
transgenes in which MAR sequences from the human
apoB
gene were arranged in a variety of ways. In agreement with previous reports, we found that a single copy of the insulating element was not sufficient for position-independent transgene expression; rather, two copies were required. However, the arrangement of the two elements within the transgene was unimportant, since chromosomal insulation was equally apparent when both copies of the insulator were upstream of the mini-
white
reporter as when the transcription unit was flanked by insulator elements. Moreover, experiments in which
apoB
3′ MAR sequences were removed from integrated transgenes in vivo by site-specific recombination demonstrated that MAR sequences were required for the establishment but not for the maintenance of chromosomal insulation. These observations are not compatible with the chromosomal loop model in its simplest form. Alternate mechanisms for MAR function in this system are proposed.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
14 articles.
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