Visible light irradiation of ethidium bromide-stained interphase nuclei causes DNA-protein linking and structural stabilization of nucleoprotein complexes.
Fixation of DNA and proteins in the isolated rat hepatocyte nuclei stained with ethidium bromide and irradiated with visible light was analyzed in this study. It was shown that irradiation results in the following modifications of higher-level nucleoprotein complexes of interphase chromatin: (1) the complexes acquire resistance to decondensing treatments, which may be indicative of the formation of links between proteins or proteins and DNA in the chromatin; (2) the linking rate for both DNA and proteins is dose dependent; (3) the irradiation induces intermolecular link formation between DNA molecules, which brings about an increase in the average molecular weight of DNA fragments; (4) some modifications (dimerization, etc.) of histones and nonhistone proteins occur; and (5) histone proteins are not effectively cross-linked to DNA. The structural stabilization of interphase chromatin is possibly mediated by free radical-based mechanisms, whereas disulfide bonds seem to play no significant role in the cross-linking.
Prusov
Andrey N
AN
Division of Electron Microscopy, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia. prusov@genebee.msu.su
Kireev
Igor I
II
Polyakov
Vladimir Yu
VY
D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000528:radiation effects; D004247:DNA / Q000737:chemistry; D004996:Ethidium / Q000737:chemistry* / Q000528:radiation effects; D007399:Interphase; D008027:Light; D008854:Microscopy, Electron; D009687:Nuclear Proteins / Q000737:chemistry; D009698:Nucleoproteins / Q000737:chemistry; D051381:Rats; D016707:Tissue Fixation / Q000379:methods*
D003432:Cross-Linking Reagents; D009687:Nuclear Proteins; D009698:Nucleoproteins; D004247:DNA; D004996:Ethidium