NUCLEAR PROTEINS IN TRANSFORMATION: AN IMMUNOLOGICAL STUDY
Abstract
Monoclonal antibodies were prepared to nuclear proteins from the 2-aminoacetyl fluorine (2-AAF) induced transplantable rat hepatoma, H$\sb2$T(L$\sp3$). Six antibodies recognized proteins specific to or enriched in tumor tissue as compared to normal adult rat tissues. Antigens 9C8 and 4.3C12 were tumor-associated in that they were detected at levels at least 5 fold higher in tumor H$\sb2$T(L$\sp3$) than in normal adult rat tissues. These antigens were elevated in all 2-AAF-induced transplantable hepatomas examined and during liver regeneration. Lower levels were found in transplantable squamous cell carcinoma, hepatoma cell lines, and HeLa cells, suggesting that the processes involving these antigens may be under-utilized by cultured cells. Antigen 1.3F12 had a similar distribution, but with a significant elevation in the 2-AAF-induced squamous cell carcinoma. This nuclear membrane antigen was not, however, detected in HeLa cells, implying species-specificity or specificity for chemically-induced cancers. Antigen 7H12 was not detected in normal adult rat tissues, was detected in only 3 of 5 transplantable tumors, but was found in all cultured cells examined. A relationship to mitogenic events required for immortalization of cells in culture could, therefore, be implied. Tumor specific antigen 5B7 appeared to be a nucleolar protein. 5B7 was present in all hepatomas and in transformed epithelial cell lines, but was not detected in normal tissues, non-transformed cell lines, squamous cell carcinoma, or transformed fibroblasts. Thus, this antigen may be associated with the transformation of specific epithelial cells. Antigen 1.3C9 was the most restricted, appearing only in hepatoma cell lines and two transplantable hepatomas. 1.3C9 may be associated with transcriptionally active chromatin since this DNA binding protein was released from nuclei by micrococcal nuclease digestion. One additional antigen, 5C3, localized to membrane-like structures and was not tumor-specific although a limited hepatic specificity was observed. By immunoblotting, anti-5C3 recognized an epitope on multiple species and did not appear to require antigen phosphorylation or glycosylation. These species may be distinct components of cell membranes and the nucleus since higher molecular weight 5C3 species were enriched in nuclei as compared to other cell fractions.
Degree
Ph.D.
Subject Area
Molecular biology
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