Bassuk J A, Sorof S
Mol Cell Biochem. 1985 Sep;68(1):49-57. doi: 10.1007/BF00219388.
Normal adult rat liver contains a nucleosomal protein that is related to the principal target polypeptide of a carcinogen in cytoplasm. Normal rat liver was found previously to contain a 14 000-dalton polypeptide that is the principal cytosolic target of the carcinogen, N-2-fluorenylacetamide (2-acetylaminofluorene; FAA), early during hepatocarcinogenesis. Elevated levels of immunohistochemically detectable target polypeptide in cytoplasm are associated with normal mitosis and carcinogen-induced hyperplasias in adult hepatocytes. A putatively related 17 500-dalton polypeptide was shown to be tightly bound to chromatin of normal liver nuclei. We report here that purified nucleosomes from normal rat liver contain the bound 17 500-dalton protein. Nuclei were digested with micrococcal nuclease, and the resultant nucleosomes were resolved into size classes by density gradient sedimentation. The monomers, dimers, and trimers of nucleosomes possessed bound 17 500-dalton polypeptide, as determined by SDS gel electrophoresis followed by immunoelectroblot analyses. Alterations in the levels of the two polypeptides were shown previously to occur during liver carcinogenesis by FAA and 3'-methyl-4-dimethylaminoazobenzene. The findings support the possibility that the 17 500-dalton polypeptide may function normally in a role related to the replication or expression of the hepatic genome, and may be connected with changes in hepatic genic activity brought about by the carcinogens.
正常成年大鼠肝脏含有一种核小体蛋白，它与致癌物在细胞质中的主要靶多肽相关。先前发现正常大鼠肝脏含有一种14000道尔顿的多肽，它是致癌物N - 2 - 芴基乙酰胺（2 - 乙酰氨基芴；FAA）在肝癌发生早期的主要胞质靶标。细胞质中免疫组织化学可检测到的靶多肽水平升高与成年肝细胞的正常有丝分裂和致癌物诱导的增生有关。一种推测相关的17500道尔顿的多肽被证明与正常肝细胞核的染色质紧密结合。我们在此报告，从正常大鼠肝脏中纯化的核小体含有结合的17500道尔顿蛋白质。用微球菌核酸酶消化细胞核，通过密度梯度沉降将所得核小体分离成不同大小类别。通过SDS凝胶电泳和免疫印迹分析确定，核小体的单体、二聚体和三聚体都含有结合的17500道尔顿多肽。先前已表明，在FAA和3'-甲基 - 4 - 二甲基氨基偶氮苯诱导的肝癌发生过程中，这两种多肽的水平会发生变化。这些发现支持了这样一种可能性，即17500道尔顿的多肽可能在与肝脏基因组复制或表达相关的正常功能中发挥作用，并且可能与致癌物引起的肝脏基因活性变化有关。
