Stabilization of non-histone proteins by copper ions does not alter chromatin properties of polythene chromosomes of Chironomus plumosus

摘要

Our previous study showed that the body of polythene chromosomes can be identified even after removal of all histones and DNA in the presence of 2 mM CuCl_2; this suggested that copper ions stabilized the bonds between non-histone proteins. In this study we tried to find out if copper ions bind with non-histone proteins reversibly or irreversibly. It is shown that the bodies of normal chromosomes and chromosomes stabilized by 2 mM CuCl_2 swell with partial disappearance of the banding pattern in a hypotonic solution (0.055 M NaCl) without copper ions. The selective removal of bivalent cations by 10 mM EDTA solution resulted in decondensation of normal polythene and stabilized chromosomes. The treatment of nuclear protein matrix of polythene chromosomes preparations with 10 mM EDTA resulted in the swelling of polythene chromosome body and disappearance of the banding pattern but their morphological organization maintained.