科研之友
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摘要
A DNA species found in tumor cells and sera of tumor bearing mice but not normal sera was cloned from tumor cells and compared to a similar species, cloned from normal tissue, in terms of sequence characteristics and DNA polymerase inhibition. This DNA species inhibits the gamma DNA polymerase and a DNA polymerase, designated the R1 polymerase, obtainable from MOPC-21 mouse myeloma tissue as previously shown by Gottlieb and co-workers. Inhibitor activity was specific with little or no effect on other DNA polymerases tested (Gottlieb et al. Cancer Res. 40: 758, 1980). In the present work, the inhibitor was obtained from MOPC-21 mouse myeloma tissue as well as from normal liver with a yield 15% of that from MOPC-21 myeloma tissue. Cloned inhibitor DNA from MOPC-21 myeloma and BALB/c liver retained its characteristic inhibitory activity. Three of four inhibitor molecules from MOPC-21 were derived from repetitive DNA sequences, suggesting amplification of repetitive sequences as part of the mechanism for production of inhibitor by this tumor. No repetitive sequences were found among the liver inhibitor molecules, suggesting a difference in the mechanism of production of these two species. These findings support the potential use of the inhibitor as a marker for certain malignancies.
