E2F1 messenger RNA is destabilized in response to a growth inhibitor in normal human keratinocytes but not in a squamous carcinoma cell line.
Keratinocyte growth arrest is characterized by a reduction in the activity and expression of E2F1. Here, we examine the role posttranscriptional processing plays in the down-regulation of E2F1 during keratinocyte growth arrest. E2F1 mRNA levels were undetectable within 8 h of exposure to the protein kinase C activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Assays of transcript stability indicated that, in untreated keratinocytes, the t 1/2 of E2F1 mRNA was 6.1 h and, in TPA-treated cells, it was 1.7 h. This destabilization was protein synthesis-dependent. In contrast, a growth inhibitor-resistant carcinoma cell line, SCC25, had a very stable E2F1 half-life that was only moderately reduced following TPA treatment. These data demonstrate that the initiation of keratinocyte growth arrest is associated with a rapid destabilization of E2F1 mRNA. These data are consistent with the proposition that inactivation of the posttranscriptional processing of important growth regulatory genes (e.g., E2F1) may contribute to neoplasia.
Saunders
N A
NA
University of Queensland Department of Medicine, Princess Alexandra Hospital, Brisbane, Australia. NSaunders@medicine.pa.uq.edu.au
Dicker
A J
AJ
Jones
S J
SJ
Dahler
A L
AL
D015152:Blotting, Northern; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004268:DNA-Binding Proteins; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D003609:Dactinomycin; D004247:DNA; D003513:Cycloheximide; D013755:Tetradecanoylphorbol Acetate