Molecular Biology and Evolution, Vol 8, 721-741, Copyright © 1991 by Society for Molecular Biology and Evolution
P Doshi, S Kaushal, C Benyajati and CI Wu
The Responder (Rsp) locus of Drosophila melanogaster, the target locus of
segregation distortion, is a satellite DNA array. This repeat array imparts
some fitness advantage to the chromosomes bearing it. In this paper, we
report the following three related molecular properties of this satellite
repeat: (1) Sequence-directed curvature--On a polyacrylamide gel,
Rsp-containing fragments migrate slower than would be predicted on the
basis of their physical sizes. The extent of migration retardation
correlates with the size and position of the Rsp sequence in a DNA
fragment, suggesting that Rsp DNA is bent. The bending is shown to be
affected by a DNA-binding drug (Hoechst 33258). (2) Nucleosome
structure--Nucleosomes associated with Rsp repeats have an unusual spacing
pattern. Instead of being spaced at approximately 190-bp intervals as is
the bulk chromatin, they are separated at approximately 240-bp intervals,
roughly the size of a dimeric Rsp repeat. The nucleosomal structure in the
Rsp region is preferentially disrupted by Hoechst 33258, whereas the bulk
chromatin appears to be insensitive to the drug. (3) Rsp-DNA binding
proteins--Gel mobility- shift assays using nuclear extracts from pupae and
end-labeled Rsp repeat demonstrate the presence of three distinct
DNA-protein complexes. Competition assays suggest that these complexes are
specific to the Rsp sequence, and two of these nucleoprotein complexes seem
to be influenced by the presence of Hoechst 33258. The observed complexes
are formed by nonhistone proteins of somatic origin and may be related to
the normal functions of Rsp, rather than to the germ-line segregation
distortion activities.
ORIGINAL ARTICLE
Molecular analysis of the responder satellite DNA in Drosophila melanogaster: DNA bending, nucleosome structure, and Rsp-binding proteins
Department of Biology, University of Rochester.
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