The Distribution of Histone Polypeptides and It's Methylated Basic Amino Acids from the Various Organs of the Rat

Author

Subhas Chakrabarty

Date of Award

12-1-1974

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical Sciences

First Advisor

John A. Duerre

Abstract

Total histones were extracted from the cerebellum, cerebrum, liver, thymus and kidney of thirty 12 day old albino rats. Polyacrylamide gel electrophoresis of twenty-five μg of histone from the various organs was carried out. The F₁, F₃, F_2a2 plus F_2b and F_2a1 components were separated into distinct bands and the relative percent of the various bands on the gels were determined by scanning the gels through a densitometer. The relative distribution of the histone components from the various organs was compared. It was found that there was no significant difference in the distribution of the histone components from the organs studied. The distribution of the various histone components does not exhibit any form of tissue heterogeneity.

The five histone components (F₁, F_2a2, F_2b, and F_2a1) from the nuclei of the cerebellum, cerebrum, liver, thymus and lidney of forty-six 15 days old albino rats, which had previously received 10 μcuries of L-[³H] lysine and 5 μcuries of L-[¹⁴C-methyl] methionine, were extracted. The animals were sacrificed 14 days after the injection of the isotopic compounds. The various histone components from the various organs were further purified by gel filtration and their purity checked by polyacrylamide gel electrophoresis. The purified histone components were hydrolyzed in 6 N HCl in vacuo and the basic amino acids fractionated on Beckman P-35 resin. Quantitation of the basic amino acids were carried out with the aid of an automatic amino acid analyzer. It was found that only F_2a1 and F₃ histones were methylated significantly. The products of methylation in the F_2a1 histones were ε-N-monomethyllysine and ε-N-dimethyllysine, with a predominance of ε-N-dimethyllysine. The products of the methylation in the F₃ histones were ε-N-monomethyllysine, ε-N-dimethyllysine and ε-N-trimethyllysine. No methylarginine was detected in any of the histones analyzed. The amount of methyllysine in the F_2a1 histones varied from 0.67 moles/mole in kidney to 0.93 moles/mole in cerebrum. Liver F_2a1 had the second highest amount of methyllysine next to cerebrum. The slightly higher methyllysine content in the cerebrum and liver may reflect the maturity of those cells in these particular organs. Since methylation of the lysyl residues occurs after the synthesis of the polypeptide chain, methylation of the histones in newly formed cells might be slightly less in older, matured ells. Pure F₃ histones were obtained by repeated gel filtration after which quantities available did not allow for complete analysis. It appears that methylation of the lysyl residues in the histone polypeptides does not contribute to tissue heterogeneity.

Recommended Citation

Chakrabarty, Subhas, "The Distribution of Histone Polypeptides and It's Methylated Basic Amino Acids from the Various Organs of the Rat" (1974). Theses and Dissertations. 468.
https://commons.und.edu/theses/468