The alternative product from the human CDKN2A locus, p14(ARF), participates in a regulatory feedback loop with p53 and MDM2.
The two distinct proteins encoded by the CDKN2A locus are specified by translating the common second exon in alternative reading frames. The product of the alpha transcript, p16(INK4a), is a recognized tumour suppressor that induces a G1 cell cycle arrest by inhibiting the phosphorylation of the retinoblastoma protein by the cyclin-dependent kinases, CDK4 and CDK6. In contrast, the product of the human CDKN2A beta transcript, p14(ARF), activates a p53 response manifest in elevated levels of MDM2 and p21(CIP1) and cell cycle arrest in both G1 and G2/M. As a consequence, p14(ARF)-induced cell cycle arrest is p53 dependent and can be abrogated by the co-expression of human papilloma virus E6 protein. p14(ARF) acts by binding directly to MDM2, resulting in the stabilization of both p53 and MDM2. Conversely, p53 negatively regulates p14(ARF) expression and there is an inverse correlation between p14(ARF) expression and p53 function in human tumour cell lines. However, p14(ARF) expression is not involved in the response to DNA damage. These results place p14(ARF) in an independent pathway upstream of p53 and imply that CDKN2A encodes two proteins that are involved in tumour suppression.
Imperial Cancer Research Fund Laboratories, P.O. Box 123, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
F J
FJ
Stott
S
S
Bates
M C
MC
James
B B
BB
McConnell
M
M
Starborg
S
S
Brookes
I
I
Palmero
K
K
Ryan
E
E
Hara
K H
KH
Vousden
G
G
Peters
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002453:Cell Cycle / Q000502:physiology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D005246:Feedback; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D017386:Sequence Homology, Amino Acid; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D009687:Nuclear Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2