Mol Cell Biol, August 1998, p. 4565-4576, Vol. 18, No. 8
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

andRobert H. Lurie Cancer Center and Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois
Received 31 March 1998/Accepted 6 May 1998
The retinoblastoma tumor suppressor gene product (pRb) is involved
in controlling cell cycle progression from G1 into S. pRb functions, in part, by regulating the activities of several
transcription factors, making pRb involved in the transcriptional
control of cellular genes. Transient-transfection assays have
implicated pRb in the transcription of several genes, including
c-fos, the interleukin-6 gene, c-myc,
cdc-2, c-neu, and the transforming growth
factor
2 gene. However, these assays place the promoter in an
artificial context and exclude the effects of far 5' upstream regions
and chromosomal architecture on gene transcription. In these
experiments, we have studied the role of pRb in the control of cell
cycle-related genes within a chromosomal context and within the context
of the G1 phase of the cell cycle. We have used adenovirus vectors to overexpress pRb in human osteosarcoma cells and breast cells
synchronized in early G1. By RNase protection assays, we have assayed the effects of this virus-produced pRb on gene expression in these cells. These results indicate that pRb is involved in the
transcriptional downregulation of the E2F-1, E2F-2, dihydrofolate reductase, thymidine kinase, c-myc, proliferating-cell
nuclear antigen, p107, and p21/Cip1 genes. However, it has no effect on the transcription of the E2F-3, E2F-4, E2F-5, DP-1, DP-2, or p16/Ink4 genes. The results are consistent with the notion that pRb controls the
transcription of genes involved in S-phase promotion. They also suggest
that pRb negatively regulates the transcription of two of the
transcription factors whose activity it also represses, E2F-1 and
E2F-2, and that it plays a role in downregulating the immediate-early
gene response to serum stimulation.
Present address: Department of Adult Oncology, Dana Farber Cancer
Institute, Boston, MA 02115.
Present address: ICGEB, Aruna Asaf Ali Marg, New Delhi 110067, India.
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