This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dehazya, P. Articles by Sirover, M. A. Search for Related Content PubMed PubMed Citation Articles by Dehazya, P. Articles by Sirover, M. A.

Regulation of Hypoxanthine DNA Glycosylase in Normal Human and Bloom's Syndrome Fibroblasts¹

Fels Research Institute and the Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140

The regulation of the base excision repair enzyme hypoxanthine DNA glycosylase was examined in normal human skin fibroblasts (NHS) and fibroblasts from a patient with Bloom's syndrome. Using randomly proliferating cells and those synchronized at specific intervals in the cell cycle, enzyme levels were shown to become elevated severalfold in a proliferation-associated manner. In NHS synchronized in G₀ by serum deprivation or in G₁ by isoleucine deprivation, maximal enzyme levels were reached prior to maximal rates of DNA synthesis. In Bloom's syndrome cells synchronized in this manner, these two activities were coincident. Cells synchronized at the G₁-S border by hydroxyurea exhibit an initial wave of DNA synthesis upon removal of the drug. The cells then undergo another DNA synthetic cycle climaxing 18–21 h after release. Maximal hypoxanthine glycosylase activity of hydroxyureasynchronized Bloom's cells was observed during the second round of DNA synthesis. However, in NHS the peak of enzyme activity was observed as early as 9 h prior to the second round of DNA synthesis. To determine if hypoxanthine glycosylase could be induced in the absence of DNA synthesis, serum-synchronized NHS were released in the presence of hydroxyurea. The results showed that inhibition of DNA synthesis did not diminish glycosylase induction which demonstrated that DNA replication was not required for glycosylase induction.

¹ This study was supported by grants to M. A. S. from the W. W. Smith Charitable Trust, the National Science Foundation (DCB-8416295), and the NIH (CA-29414) and by grants to the Fels Research Institute from the NIH (CA 12227) and from the American Cancer Society (SIG-6).

² Present address: Merrell Dow Research Institute, Cincinnati, OH 45215.

³ To whom requests for reprints should be addressed.

Received 10/25/85. Revised 2/10/86. Accepted 4/16/86.