The rat ARF protein is translated from two closely spaced ATG start codons and can transcriptionally activate p53 in the absence of p53 protein stabilization.
We have analyzed the transcriptional start sites of the rat ARF gene and the amino acid sequence of the rat ARF tumor suppressor protein. The 5' end of the ratARF gene is similar to that of a number of cellular housekeeping genes in that it is CG-rich and does not contain an upstream TATA box motif to define a precise transcriptional start site. The transcription of the rat ARF gene is initiated at multiple start sites with one major start site accounting for 41% of transcription. The rat ARF protein contains two methionine ATG codons at its amino terminus separated by 10 amino acids. The translation of the major endogenous ARF protein species is initiated from the upstream methionine ATG codon. The upstream methionine ATG codon is predominantly used, despite the fact that it is both very close to the major transcriptional start site (6 bases downstream) and is in a less favorable nucleic acid sequence context than the downstream ATG, relative to the ideal sequence postulated for efficient initiation of translation. The downstream, inefficient rat ARF ATG is equivalent to the major mouse ARF ATG start codon. Both of these closely spaced ATGs can be utilized as a translational start codon to produce a nucleolar-localized ARF protein which can induce a p53-dependent inhibition of cell division and transcriptional activation of p53 in the absence of p53 stabilization.
Hunt
Abigail E
AE
UCSF Cancer Research Institute, San Francisco, California 94115, USA.
Moule
Madeleine G
MG
Fried
Mike
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002455:Cell Division; D002478:Cells, Cultured; D018387:Codon, Initiator / Q000235:genetics; D008715:Methionine / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000235:genetics; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism*
D018387:Codon, Initiator; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; C508715:p19(ARF) protein, rat; D008715:Methionine