The adenovirus E1A protein overrides the requirement for cellular ras in initiating DNA synthesis.
The adenovirus E1A protein can induce cellular DNA synthesis in growth-arrested cells by interacting with the cellular protein p300 or pRb. In addition, serum- and growth factor-dependent cells require ras activity to initiate DNA synthesis and recently we have shown that Balb/c 3T3 cells can be blocked in either early or late G1 following microinjection of an anti-ras antibody. In this study, the E1A 243 amino acid protein is shown through microinjection not only to shorten the G0 to S phase interval but, what is more important, to override the inhibitory effects exerted by the anti-ras antibody in either early or late G1. Specifically, whether E1A is co-injected with anti-ras into quiescent cells or injected 18 h following a separate injection of anti-ras after serum stimulation, it efficiently induces cellular DNA synthesis in cells that would otherwise be blocked in G0/G1. Moreover, injection of a mutant form of E1A that can no longer associate with p300 is just as efficient as wild-type E1A in stimulating DNA synthesis in cells whose ras activity has been neutralized by anti-ras. The results presented here show that E1A is capable of overriding the requirement of cellular ras activity in promoting the entry of cells into S phase. Moreover, the results suggest the possibility that pRb and/or pRb-related proteins may function in a ras-dependent pathway that enables E1A to achieve this activity.
Stacey
D W
DW
Department of Molecular Biology, Cleveland Clinic Foundation, OH 44195.
Dobrowolski
S F
SF
Piotrkowski
A
A
Harter
M L
ML
D016475:3T3 Cells; D017500:Adenovirus E1A Proteins / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis*; D050881:E1A-Associated p300 Protein; D016193:G1 Phase / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008845:Microinjections; D009687:Nuclear Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D016192:Resting Phase, Cell Cycle / Q000502:physiology; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism
D017500:Adenovirus E1A Proteins; D000911:Antibodies, Monoclonal; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse; D016283:Proto-Oncogene Proteins p21(ras)