TY - JOUR
T1 - Studies on the distribution of O6-methylguanine-dna methyltransferase in rat
AU - Gil-Ja Jun, Jun
AU - Jai-Youl Ro, Ro
AU - Myung Hee Kim, Hee Kim
AU - Gil-Hong, Park
AU - Woon Ki Paik, Ki Paik
AU - Magee, Peter N.
AU - Sangduk, Kim
N1 - Funding Information:
Acknowledgements-Thisw ork was supportedi n part by Grants CA12226 and CA 12227fr om tie National-Cancer Institute, BNS-8119666fr om the National ScienceF oun-dation, and the Illman Fund for Cancer Researchf rom Temple University, Philadelphia,P A, U.S.A.
PY - 1986/2/1
Y1 - 1986/2/1
N2 - O6-Methylguanine-DNA methyltransferase, a DNA repair enzyme which transfers the methyl group of O6-methylguanine residue to a cysteinyl residue in the methyltransferase itself, was examined in rat organs by quantifying the S-methylcysteine formed in the methyl acceptor protein. Among the various organs examined, the spleen exhibited the highest enzyme specific activity followed by the thymus, liver, lung and testis. Brain had the lowest activity. The patterns of subcellular distribution of the methyltransferase in spleen and liver were different: while 75-80% of the activity was present in the nuclear fraction of the spleen, 54% of the activity in the liver was found in the nuclei and 35% in the cytosolic fraction. Forty-five and thirty-five percent of the total nuclear enzyme activity could be extracted with 1 M and 2 M NaCl solutions, respectively, indicating that the repair enzyme is not tightly bound to the nuclear matrix. When isolated nuclei were incubated with [methyl-3H]DNA substrate and subsequently fractionated into histone and non-histone protein fractions, over 90% of the radioactivity was coeluted on a Bio-Rex 70 column with the non-histone fraction and only a negligible amount of radioactivity was found to be associated with the histone fraction. The molecular mass of the [methyl-3H]methyltransferase in the non-histone fraction was determined to be 23,000, and its pI value was found to be 6.6 by two-dimensional polyacrylamide gel electrophoresis.
AB - O6-Methylguanine-DNA methyltransferase, a DNA repair enzyme which transfers the methyl group of O6-methylguanine residue to a cysteinyl residue in the methyltransferase itself, was examined in rat organs by quantifying the S-methylcysteine formed in the methyl acceptor protein. Among the various organs examined, the spleen exhibited the highest enzyme specific activity followed by the thymus, liver, lung and testis. Brain had the lowest activity. The patterns of subcellular distribution of the methyltransferase in spleen and liver were different: while 75-80% of the activity was present in the nuclear fraction of the spleen, 54% of the activity in the liver was found in the nuclei and 35% in the cytosolic fraction. Forty-five and thirty-five percent of the total nuclear enzyme activity could be extracted with 1 M and 2 M NaCl solutions, respectively, indicating that the repair enzyme is not tightly bound to the nuclear matrix. When isolated nuclei were incubated with [methyl-3H]DNA substrate and subsequently fractionated into histone and non-histone protein fractions, over 90% of the radioactivity was coeluted on a Bio-Rex 70 column with the non-histone fraction and only a negligible amount of radioactivity was found to be associated with the histone fraction. The molecular mass of the [methyl-3H]methyltransferase in the non-histone fraction was determined to be 23,000, and its pI value was found to be 6.6 by two-dimensional polyacrylamide gel electrophoresis.
UR - http://www.scopus.com/inward/record.url?scp=0022560577&partnerID=8YFLogxK
U2 - 10.1016/0006-2952(86)90208-X
DO - 10.1016/0006-2952(86)90208-X
M3 - Article
C2 - 3947377
AN - SCOPUS:0022560577
SN - 0006-2952
VL - 35
SP - 377
EP - 384
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 3
ER -