Experimental modification of the “tertiary structure” of chromosomes in human lymphocytes: The effects of polyanionic substances and hypertonic salt solutions

Abstract

The chromosomes in G 0 lymphocytes in freshly drawn human blood react to radiation as though they were single-stranded: chromosome, rather than chromatid, aberrations are induced. Treatment of the cells with glycerol or urea has previously been found to change this response. The present experiments show that treatment with the polyanionic substances spermine or spermidine can cause loosening of chromosomal subunits in G 1, but not G 0, lymphocytes. Cleland's reagent, which breaks disulfide bonds, and EDTA, which chelates divalent metal ions, do not affect the structure. The response of chromosomes in very late G 1 cells can also be modified. At this point in the cell cycle the subunits separate spontaneously to react to radiation by forming chromatid aberrations. Treatment with hypertonic salt solutions to induce plasmolysis tightens the tertiary structure so that now fewer chromatid aberrations can be induced.