STRUCTURAL FEATURES OF CHROMATIN ORGANIZATION OF 3C6/C7 INTERBAND IN DROSOPHILA MELANOGASTER POLYTENE CHROMOSOMES
Andreenkov O.V., Volkova E.I., Semeshin V.F., Zhimulev I.F., Demakov S.A.
Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russia;
e-mail: demakov@mcb.nsc.ru
This article presents an analysis of the causes of chromatin decompaction of interbands in Drosophila polytene chromosomes. On the example of interband 3C6/C7 of X
chromosome we investigate the ability of different DNA segments from the region to form an interband in a new genetic environment. Site-specific FLP recombination between two
transposons with FRT-sites, allows introducing the DNA fragments from the interband 3C6/C7 into pICon(dv) transposon located in cytologically well-characterized 84F region of
chromosome 3 followed by electron microscopic analysis of changes in the region, caused by insertion of the DNA fragments into the transposon. Thus, it was shown that the insertion of
DNA fragment 276 bp in length from 3C6/C7 region into the pICon(dv) transposon leads to the formation of a new interband between two thin bands which are represented by material
of the transposon. To date, the DNA fragment is minimal known sequence that is necessary and sufficient for interband formation. In addition, the sequence containing three tandemly
repeated copies of DNA fragment 0,9 kb in length including a fragment of 276 bp from the interband 3C6/C7 was integrated in the transposon. The presence of additional copies of the
DNA fragment did not change the morphology of the resulting interband. It was shown that the sites of hypersensitivity to DNase I saved in interbands formed in a new genetic
environment.
The data obtained allow to start an analysis of specific factors (proteins, DNA motifs, etc), which are determine a formation of decompacted chromatin state in certain interband
region and, as a whole, chromomeric organization of interphase chromosomes in Drosophila.
Key words: transposons, site-specific recombination, genome transformation, chromatin, interband, polytene chromosomes
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