Role of the alternative INK4A proteins in human keratinocyte senescence: evidence for the specific inactivation of p16INK4A upon immortalization.
The INK4A locus on human chromosome 9p21 encodes two genes that have been implicated in replicative senescence and tumor suppression, p16INK4A and p14ARF. In contrast to p16INK4A, which is up-regulated to high levels, we were unable to detect p14ARF protein in senescent human keratinocytes. Also, p53, an established target of p14ARF, did not increase, suggesting that p14ARF is not instrumental in human keratinocyte senescence. In neoplastic keratinocyte cultures, p16INK4A inactivation was invariably associated with the immortal phenotype, and there was evidence for the inactivation of p16INK4A, independent of p14ARF, in 6 of 10 lines that lacked large homozygous deletions. In contrast, we failed to detect exon 1beta mutations or p16INK4A-independent deletions. These results emphasize the previously proposed role for p16INK4A in human keratinocyte senescence but do not rule out a supporting role for p14ARF inactivation.
Munro
J
J
Beatson Institute for Cancer Research, Cancer Research Campaign Beatson Laboratories, Glasgow, United Kingdom.
Stott
F J
FJ
Vousden
K H
KH
Peters
G
G
Parkinson
E K
EK
D016475:3T3 Cells; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D005091:Exons / Q000235:genetics; D017353:Gene Deletion; D006801:Humans; D015603:Keratinocytes / Q000502:physiology*; D051379:Mice; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011506:Proteins; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53