This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Juan, G. Articles by Darzynkiewicz, Z. Search for Related Content PubMed PubMed Citation Articles by Juan, G. Articles by Darzynkiewicz, Z.

Correlation between DNA Replication and Expression of Cyclins A and B1 in Individual MOLT-4 Cells¹

The Cancer Research Institute, New York Medical College, Valhalla, New York 10595

Cyclins A and B1 activate cyclin-dependent kinases CDK2 and CDC2, which regulate cell progression through S and G₂. Expression of these cyclins is generally measured in populations of synchronized cells, by immunoblotting. Such studies neither provide information regarding intercellular variability in cyclin expression nor yield precise data on a time relationship between initiation and termination of DNA replication in relation to cyclin expression. Furthermore, cell synchronization by DNA polymerase inhibitors or excess of thymidine induces cell growth imbalance and alters expression of cyclins, thereby introducing an experimental bias. Using a novel flow cytometric method of detection of incorporated bromodeoxyuridine (BrdUrd) in the present study, we have been able to correlate expression of immunocytochemically discerned cyclins A and B1 with incorporation of BrdUrd and the cell cycle position of individual MOLT-4 cells. On the basis of differences in amount of incorporated BrdUrd and DNA content, the following cohorts of cells in narrow windows of the cell cycle were identified: (a) cells initiating and (b) terminating DNA replication during a 1-h pulse of BrdUrd; (c) cells replicating DNA throughout the duration of BrdUrd pulse; (d) G₁ cells; and (e) G₂ cells that remained in G₂ for at least 1 h after exiting S phase. These populations were characterized with respect to expression of cyclins A and B1. Expression of cyclin A was an early event of S phase, and 84% of cells entering S phase during 1 h of exposure to BrdUrd were already cyclin A positive. More than 95% of S-phase cells, as well as the cells exiting S during BrdUrd pulse, were also cyclin A positive. The maximal rate of accumulation of cyclin A was seen during the first hour of progression through S phase. In contrast, the maximal accumulation rate of cyclin B1 showed cells during the first hour of progression through G₂. A strong correlation between expression of cyclin A and the rate of DNA replication, estimated by the degree of BrdUrd incorporation (r = 0.99), was observed.

¹ This work was supported by National Cancer Institute Grant RO1 28704 and by "This Close" Foundation for Cancer Research. G. J. is on leave from the University of Valencia, Spain. X. L. is on leave from Tongji University, Wuhan, China.

² To whom requests for reprints should be addressed, at The Cancer Research Institute, New York Medical College, 100 Grasslands Road, Elmsford, NY 10523. Phone: (914) 347-2801; Fax: (914) 347-2804; E-mail: darzynk@nymc.edu.

Received 10/15/96. Accepted 1/17/97.

This article has been cited by other articles:

				F. Wolter, B. Akoglu, A. Clausnitzer, and J. Stein Downregulation of the Cyclin D1/Cdk4 Complex Occurs during Resveratrol-Induced Cell Cycle Arrest in Colon Cancer Cell Lines J. Nutr., August 1, 2001; 131(8): 2197 - 2203. [Abstract] [Full Text] [PDF]

				G. Juan and C. Cordon-Cardo Intranuclear Compartmentalization of Cyclin E during the Cell Cycle: Disruption of the Nucleoplasm-Nucleolar Shuttling of Cyclin E in Bladder Cancer Cancer Res., February 1, 2001; 61(3): 1220 - 1226. [Abstract] [Full Text]

				H. Zhu, A. R. Boobis, and N. J Gooderham The Food-derived Carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine Activates S-Phase Checkpoint and Apoptosis, and Induces Gene Mutation in Human Lymphoblastoid TK6 Cells Cancer Res., March 1, 2000; 60(5): 1283 - 1289. [Abstract] [Full Text]

				T.-c. Hsieh, G. Juan, Z. Darzynkiewicz, and J. M. Wu Resveratrol Increases Nitric Oxide Synthase, Induces Accumulation of p53 and p21WAF1/CIP1, and Suppresses Cultured Bovine Pulmonary Artery EndothelialCell Proliferation by Perturbing Progression through S and G2 Cancer Res., June 1, 1999; 59(11): 2596 - 2601. [Abstract] [Full Text] [PDF]