title: Association of actin with the nuclear matrix from bovine lymphocytes.
abstract: Nuclear matrix prepared from bovine lymphocytes contained a significant amount of actin. Both nuclear matrix actin and rabbit muscle actin showed the same electrophoretic mobility on SDS-gel. The matrix-associated actin could be separated into three isoproteins which may correspond to alpha-, beta- and gamma-actin. The most acidic spot of these isoproteins co-migrated with rabbit muscle actin (alpha-actin) on two-dimensional electrophoresis. The amino-acid composition of the nuclear matrix actin was closely related to that of rabbit muscle and to that of porcine brain actin. Moreover, the actin filaments, treated with 0.75 M guanidine hydrochloride, changed from the polymerized form of the nuclear matrix actin into a monomeric form (G-actin), which had strong inhibitor activity against pancreatic DNase I. From this inhibition, the actin content of the nuclear matrix was estimated to be about 12% of total matrix protein. When the nuclear matrix was digested with trypsin, the bulk of matrix protein was hydrolyzed, but about 80% of the actin remained associated with sphere structures (trypsin-treated nuclear matrix) precipitable by low speed centrifugation. SDS-gel analysis revealed that actin was one of the major components of the trypsin-treated nuclear matrix, which had a similar size and structure as the untreated nuclear matrix. The fibrogranular structure and residual nucleoli of the original nuclear matrix were well preserved against trypsin digestion; however, the peripheral lamina was removed. These results indicate that the matrix-associated actin is localized predominantly in the matrix interior, where it presumably interacts closely with the fibrogranular structure and/or the residual nucleoli.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism*; D003850:Deoxyribonuclease I; D004591:Electrophoresis, Polyacrylamide Gel; D004706:Endodeoxyribonucleases / Q000037:antagonists & inhibitors; D008214:Lymphocytes / Q000166:cytology*; D008854:Microscopy, Electron; D008970:Molecular Weight; D051381:Rats; D014357:Trypsin / Q000378:metabolism
chemical_list: D000199:Actins; D000596:Amino Acids; D004706:Endodeoxyribonucleases; D003850:Deoxyribonuclease I; D014357:Trypsin