Rb and p130 regulate RNA polymerase I transcription: Rb disrupts the interaction between UBF and SL-1.
We have previously demonstrated that the protein encoded by the retinoblastoma susceptibility gene (Rb) functions as a regulator of transcription by RNA polymerase I (rDNA transcription) by inhibiting UBF-mediated transcription. In the present study, we have examined the mechanism by which Rb represses UBF-dependent rDNA transcription and determined if other Rb-like proteins have similar effects. We demonstrate that authentic or recombinant UBF and Rb interact directly and this requires a functional A/B pocket. DNase footprinting and band-shift assays demonstrated that the interaction between Rb and UBF does not inhibit the binding of UBF to DNA. However, the formation of an UBF/Rb complex does block the interaction of UBF with SL-1, as indicated by using the 48 kDa subunit as a marker for SL-1. Additional evidence is presented that another pocket protein, p130 but not p107, can be found in a complex with UBF. Interestingly, the cellular content of p130 inversely correlated with the rate of rDNA transcription in two physiological systems, and overexpression of p130 inhibited rDNA transcription. These results suggest that p130 may regulate rDNA transcription in a similar manner to Rb.
Hannan
K M
KM
Henry Hood Research Program, Weis Center for Research, Geisinger Clinic, 100 N. Academy Ave., Danville, Pennsylvania, PA 17822 USA.
Hannan
R D
RD
Smith
S D
SD
Jefferson
L S
LS
Lun
M
M
Rothblum
L I
LI
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism / Q000502:physiology*; D035463:Pol1 Transcription Initiation Complex Proteins; D011506:Proteins; D012318:RNA Polymerase I / Q000096:biosynthesis / Q000235:genetics*; D016160:Retinoblastoma Protein / Q000502:physiology*; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D035463:Pol1 Transcription Initiation Complex Proteins; D011506:Proteins; C493844:RBL1 protein, human; C493837:RBL2 protein, human; C489485:Rbl1 protein, mouse; C493838:Rbl2 protein, mouse; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; C091131:TAF1A protein, human; C484259:Taf1a protein, mouse; D014157:Transcription Factors; C063844:transcription factor UBF; C063660:transcription initiation factor TIF-IB; D012318:RNA Polymerase I