Regulation of RB transcription in vivo by RB family members.
In cancer cells, the retinoblastoma tumor suppressor RB is directly inactivated by mutation in the RB gene or functionally inhibited by abnormal activation of cyclin-dependent kinase activity. While variations in RB levels may also provide an important means of controlling RB function in both normal and cancer cells, little is known about the mechanisms regulating RB transcription. Here we show that members of the RB and E2F families bind directly to the RB promoter. To investigate how the RB/E2F pathway may regulate Rb transcription, we generated reporter mice carrying an eGFP transgene inserted into a bacterial artificial chromosome containing most of the Rb gene. Expression of eGFP largely parallels that of Rb in transgenic embryos and adult mice. Using these reporter mice and mutant alleles for Rb, p107, and p130, we found that RB family members modulate Rb transcription in specific cell populations in vivo and in culture. Interestingly, while Rb is a target of the RB/E2F pathway in mouse and human cells, Rb expression does not strictly correlate with the cell cycle status of these cells. These experiments identify novel regulatory feedback mechanisms within the RB pathway in mammalian cells.
Burkhart
Deborah L
DL
Department of Pediatrics, Stanford Medical School, 269 Campus Drive, CCSR1215, Stanford, CA 94305, USA.
Ngai
Lynn K
LK
Roake
Caitlin M
CM
Viatour
Patrick
P
Thangavel
Chellappagounder
C
Ho
Victoria M
VM
Knudsen
Erik S
ES
Sage
Julien
J
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000502:physiology; D017930:Genes, Reporter; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107 / Q000235:genetics / Q000378:metabolism*; D050717:Retinoblastoma-Like Protein p130 / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D050684:E2F Transcription Factors; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130