title: Protein A24 lyase activity in nucleoli of thioacetamide-treated rat liver releases histone 2A and ubiquitin from conjugated protein A24.
abstract: Isolated liver nucleoli from rats treated for 3 days with thioacetamide contained an enzyme activity which specifically degraded conjugate protein A24. Two-dimensional polyacrylamide gel electrophoresis indicated that the amount of protein A24 in chromatin decreased during incubation at 37 degrees C for 60 min with these nucleoli. Concomitantly, a marked increase was found in the content of free ubiquitin, the nonhistone component of protein A24. Incubation of 3H-labeled protein A24 with the thioacetamide-treated liver nucleoli resulted in the linear release of 3H-labeled histone 2A and 3H-free ubiquitin in the presence of phenylmethanesulfonyl fluoride (PMSF) for 2 h. Pretreatment of the nucleoli with trypsin or by heating at 80 degrees C for 10 min inhibited their ability to cleave protein A24. Protein A24 lyase catalyzes the reaction: protein A24 leads to histone 2A plus ubiquitin.
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006657:Histones / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008190:Lyases / Q000378:metabolism*; D009698:Nucleoproteins / Q000378:metabolism*; D051381:Rats; D013853:Thioacetamide / Q000494:pharmacology*; D014452:Ubiquitins
chemical_list: D000081:Acetamides; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D009698:Nucleoproteins; D014452:Ubiquitins; C021645:chromatin conjugate protein A24; D013853:Thioacetamide; D008190:Lyases; C030018:protein A24 lyase