A simple method for the application of two samples to polyacrylamide gel for comparative electrophoresis

Studies on the tissue specificity of the high-mobility-group non-histone chromosomal proteins from calf

The high-mobility-group (HMG) non-histone chromosomal proteins from calf thymus, liver, spleen and kidney were extracted, and fractionated by CM-Sephadex chromatography and trichloroacetic acid precipitation. The isolated proteins HMG 1, HMG 2 and HMG 17 from the tissues were compared by polyacrylamide-gel electrophoresis, isoelectric focusing and amino acid analysis. The results show that the three proteins are very similar in the tissues studied, implying a lack of tissue specificity.

Studies on the degradation of high mobility group non-histone chromosomal proteins

During the isolation of high mobility group non-histone proteins from calf thymus chromatin by methods described previously (e.g. Goodwin, G.H., Nicolas, R.H. and Johns, E.W. (1975) Biochim. Biophys, Acta. 405, 280--291) protein degradation occurs resulting in a number of proteins appearing in the chromatin extracts which are not present in high mobility group protein preparations in which proteolysis has been completely inhibited. These extra proteins, formerly numbered high mobility group proteins 3, 5, 6 and 8, are thus probably degradation products of other nuclear proteins, produced during the isolation procedure. From the amino acid analyses, tryptic peptides and N-terminal sequences, it is concluded that high mobility group protein 3 is probably a degradation product of high mobility group protein 1. The amino acid analysis of high mobility group protein 8 is very similar to that of the N-terminal half of histone H1 suggesting that high mobility group protein 8 is a degradation product of this histone.

Are the high mobility group non-histone chromosomal proteins associated with 'active' chromatin?

When 10--20% of the DNA in thymus and liver nuclei is rendered acid-soluble by DNAase I digestion, under conditions which may be expected to specifically degrade away most of the transcribed sequences, very little of the high-mobility-group non-histone proteins are released from the nuclei. Therefore, high-mobility-group proteins are probably not specifically associated with this portion of the genome.

The interaction of nonhistone chromosomal proteins HMG1 and HMG2 with subfractions of H1 histone immobilized on agarose

Chromatographically isolated subfractions of calf thymus H1 histone have been covalently coupled to agarose beads and tested for their ability to form complexes with the non-histone proteins HMG1 and HMG2 (High Mobility Group proteins, Walker, J.M., Goodwin, G.H. and Johns, E.W. (1976) Eur. J. Biochem. 62, 461-469). When a mixture of HMG1 and HMG2 is passed through a column of H1 histone-agarose, the HMG2 does not bind. HMG1 does bind and can be eluted from the column with NaCl in the range of 0.05 M--0.15 M. The NaCl concentration required to elute HMG1 from each of the three H1 histone subfraction coulmns is different, suggesting that HMG1 has a different binding affinity for the three H1 histone subfractions.

An improved large scale fractionation of high mobility group non-histone chromatin proteins

1. Methodology is presented for the large scale preparation and fractionation of high mobility group proteins from calf thymus chromatin. The total high mobility group protein from approx. 1 kg calf thymus tissue can be separated into five fractions by CM-Sephadex C25 ion-exchange chromatography. High mobility group proteins 1 and 2 comprise two fo the fractions. From a third fraction two more chromatin proteins, protein 3 and 17, can be isolated by trichloroacetic acid precipitation and CM-cellulose chromatography at pH 5.5. 2. The four proteins thus purified are lysine-rich proteins. Proteins 1 and 2 are additionally characterised by their high contents of acidic amino acids, as described previously (Goodwin, G. H. and Johns, E. W. (1973) Eur. J. Biochem. 40, 215-219). Proteins 3 and 17, having lower contents of acidic amino acids, are basic proteins similar to the histones. All four proteins exhibit single N-terminal amino acids; glycine is the N-terminal group of proteins 1, 2 and 3; protein 17 has a proline N-terminal amino acid. The proteins are not highly phosphorylated nor are they associated with appreciable quantities of nucleic acid.