Electrophoretic pattern of the polypeptide component in the tight DNA-protein complexes in rat and chicken tissues and its partial characterisation in rat liver

Tightly bound to DNA proteins (TBP) are a protein group that remain attached to DNA with covalent or non-covalent bonds after its deproteinisation. The distribution of TBP in genes reflects the type of cell differentiation. It has been hypothesised that TBP binding is involved in regulation of gene expression. Early studies reported uniformity of the TBPs from different sources. Later it was shown that TBPs obtained from DNA, isolated in mild conditions from evolutionary distant species, are different. Application of chloroform DNA extraction without use of externally added enzymes enabled us to reveal differences in the TBP spectrum in plant organs and changes of this spectrum in the course of plant development. The goal of this work was to study the electrophoretic pattern of the polypeptide component in the tight DNA-protein complexes in organs of animals: a mammal (rat) and a bird (chicken). Rat thymus TBPs were represented by 70 and 60 kDa proteins, and the same polypeptides were observed also in brain and skeletal muscles. Kidney TBPs were represented by 85, 70, 65, 60 and 37 kDa polypeptides; 85, 77, 70, 60, 50 and 37 kDa TBPs were characteristic of liver. Numerous minor peptides were observed in all samples studied. The spectrum of chicken liver and blood TBPs differed in distribution of proteins of 25-35 kDa. Mass-spectrometry of 14 bands from rat liver TBP gel revealed 43 different proteins. Chromatin modifying proteins and repair enzymes, transcription factors, serpins, ATPase, kinases and enzymes of ubiquitin-proteasome pathway were found among the TBPs. Thus, TBPs appear to be a vast protein group involved in several intranuclear processes. It is hypothesised that numerous functions ascribed to the nuclear matrix are performed in the TBP complexes.