SSP染色体のComputerized Mapによるクロマチン活性部位の解析

Abstract

Surface-spread polytene (SSP) chromosomes of salivary glands from late third-instar larvae were used for the construction of an electron microscopic (EM) photo map of the entire genome of D. melanogaster Oregon Q₂. The SSP chromosomes were spread by surface tension, according to the method of the Kalisch group, show more additional bands and interbands than the squashed chromosomes. Recent advances in the molecular mapping of Drosophila DNA have raised the necessity for the fine chromosome map. In this investigation we drew the computerized SSP EM map by using our original computer program, and localized DNaseⅠ-gold binding sites on SSP 3L chromosome. The subdivision 68C and 71C, including glue protein genes, were markedly bound with DNaseⅠ-gold, and the most of DNaseⅠ-gold were found peculiarly to the approximately 30 nm chromatin fiber. This suggested that the DNaseⅠ-gold binding fibers retain the loosened solenoid structure, which is different three-dimensionally from the conventional solenoid type.