P130 and its truncated form mediate p53-induced cell cycle arrest in Rb(-/-) Saos2 cells.
In the present study, we investigate the mechanism of how p53 induces growth arrest in Rb-defective Saos2 cells that express temperature-sensitive mutant p53 (ts p53). The activation of p53 at a permissive temperature (32.5 degrees C) induces the cell cycle arrest at both the G1 and G2 stages. The induction of several p53-responsive genes as well as a small form of p130 (S-p130) was detected upon p53 activation. S-p130 retained the functions as a pocket protein and was dominant over p130 at the protein level after 36 h at 32.5 degrees C. A canonical p53 binding site was identified in intron 4 of p130. Furthermore, a novel p53-inducible transcript containing a partial intron 4 sequence downstream of the p53 binding site and exon 5 of p130 was detected by RT-PCR, suggesting S-p130 is induced by p53 at transcriptional level. The results from gel shift assay and immunoprecipitation showed that S-p130 as well as p130 formed complexes with both E2F1 and E2F4 at a permissive temperature. Moreover, the transient expression of E1A (12S) and E2F1 effectively abrogated p53-induced cell cycle arrest. These results strongly suggested that p130 and its truncated form might substitute Rb in mediating p53-induced cell cycle arrest in Rb(-/-) Saos2 cells.
Gao
Chong-Feng
CF
Department of Molecular Cellular Oncology, Graduate School, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan.
Ren
Shuo
S
Wang
Jingfei
J
Zhang
Sheng-Liang
SL
Jin
Feng
F
Nakajima
Takuma
T
Ikeda
Masaaki
M
Tsuchida
Nobuo
N
D001483:Base Sequence; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050704:E2F4 Transcription Factor; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011233:Precipitin Tests; D011506:Proteins; D016160:Retinoblastoma Protein / Q000235:genetics / Q000502:physiology*; D050717:Retinoblastoma-Like Protein p130; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D010750:Phosphoproteins; D011506:Proteins; C493837:RBL2 protein, human; D016160:Retinoblastoma Protein; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53