The retinoblastoma gene product regulates Sp1-mediated transcription.
We have demonstrated that the retinoblastoma gene product (Rb) can positively regulate transcription from the fourth promoter of the insulinlike growth factor II gene. Two copies of a motif (the retinoblastoma control element) similar to that found in the human c-fos, transforming growth factor beta 1, and c-myc promoters are responsible for conferring Rb regulation to the fourth promoter of the insulinlike growth factor II gene. We have shown that the transcription factor Sp1 can bind to and stimulate transcription from the retinoblastoma control element motif. Moreover, by using a GAL4-Sp1 fusion protein, we have directly demonstrated that Rb positively regulates Sp1 transcriptional activity in vivo. These results indicate that Rb can function as a positive regulator of transcription and that Sp1 is one potential target, either directly or indirectly, for transcriptional regulation by Rb.
Kim
S J
SJ
Laboratory of Chemoprevention, National Cancer Institute, Bethesda, Maryland 20892.
Onwuta
U S
US
Lee
Y I
YI
Li
R
R
Botchan
M R
MR
Robbins
P D
PD
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D051379:Mice; D008907:Mink; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D016160:Retinoblastoma Protein / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor / Q000502:physiology*; D014157:Transcription Factors; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D009838:Oligodeoxyribonucleotides; D016160:Retinoblastoma Protein; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D007335:Insulin-Like Growth Factor II