Chromatin association and DNA binding properties of the c-fos proto-oncogene product.
As a first step in the analysis of the molecular function of the nuclear c-fos proto-oncogene product we have studied its subnuclear localization in serum-stimulated mouse fibroblasts where it forms a non-covalent, apparently monodisperse complex with another nuclear protein, p39. The c-fos/p39 complex is almost quantitatively released from intact nuclei by DNasel or micrococcus nuclease treatment under conditions where only a minor fraction of DNA and nuclear proteins is released. In gel filtration experiments, c-fos/p39 comigrates with chromatin and seems to be associated with regions of increased DNasel accessibility. c-fos/p39 is bound to chromatin by electrostatic forces of moderate strength since greater than 90% of the complex can be eluted from nuclei at 0.4 M NaCl. In vitro, the c-fos/p39 complex in nuclear extracts binds to double- and single-stranded calf thymus DNA, suggesting that the association of c-fos/p39 with chromatin is at least in part due to its interaction with DNA. In agreement with this conclusion, c-fos/p39 is released from nuclei by incubation with tRNA, presumably due to competition for binding sites. Our observations are compatible with the hypothesis that c-fos may play a role in the regulation of gene expression.
D000818:Animals; D002458:Cell Fractionation; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism* / Q000648:ultrastructure; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos; D011519:Proto-Oncogenes
D002843:Chromatin; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D004247:DNA