DNA polymerase beta in human thyroid of Graves' disease and thyroid tumors

We have shown that the level of DNA polymerase beta of rat adrenal cortex is regulated by pituitary trophic hormones and may correlate with their endocrine function. Here we measured DNA polymerase beta activity in human thyroid tissues of various benign and malignant thyroid disorders in order to verify the correlation between DNA polymerase beta activity and endocrine function. In Graves' disease (hyperfunction), the level of DNA polymerase beta per cell was three times higher than in normal thyroid, while in undifferentiated thyroid carcinomas this enzyme level was lower than normal. Furthermore, DNA polymerase beta in the crude extracts of cancer cells showed larger molecular forms, ranging from five to 12S, upon sucrose gradient sedimentation. These observations further support the hypothesis that the activity of DNA polymerase beta correlates, in part, with the functional level of the endocrine organ and with cell differentiation.