One INK4 gene and no ARF at the Fugu equivalent of the human INK4A/ARF/INK4B tumour suppressor locus.
The INK4A/ARF/INK4B locus, conserved in mammals, encodes three polypeptides that regulate cell proliferation via the pRb and p53 tumour suppressor pathways. The locus is mutated in many cancers. The related, tandemly-linked INK4A and INK4B genes encode the p16(INK4A) and p15(INK4B) members of the INK4 family of cyclin-dependent kinase inhibitors which block phosphorylation of pRb, whereas the third product, ARF, derived from an alternative reading frame of INK4A, regulates p53 activity. We assessed the status of this unusual locus in the puffer fish, Fugu rubripes, and identified two INK4 genes using degenerate PCR and hybridization analyses. Sequence conservation and conservation of synteny between human and Fugu predict one gene to be an INK4A or INK4B homologue and the other an INK4D homologue. Analysis of the Fugu INK4A/B gene and the surrounding 40-kb of genomic DNA did not reveal the presence of any ARF-encoding potential or another related INK4 gene. We conclude that the gene duplication event that generated adjacent INK4A and INK4B genes and the association of ARF with the ancestral INK4A gene occurred after the divergence of the lineage leading to mammals from fish. Thus, unlike mammals, the fish p53 and pRb tumour suppressor pathways are not regulated by a single locus.
Gilley
J
J
Eukaryotic Gene Organisation and Expression Laboratory, Imperial Cancer Research Fund, Lincoln's Inn Fields, London, WC2A 3PX, UK.
Fried
M
M
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D003360:Cosmids; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D050764:Cyclin-Dependent Kinase Inhibitor p19; D003532:Cyprinodontiformes / Q000235:genetics; D019143:Evolution, Molecular; D005399:Fishes / Q000235:genetics; D020440:Gene Duplication; D015723:Gene Library; D019942:Genes, p16; D006801:Humans; D008322:Mammals / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D023741:Takifugu / Q000235:genetics*; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics*; D025521:Tumor Suppressor Proteins
C493966:CDKN2B protein, human; C493974:CDKN2D protein, human; C493968:Cdkn2b protein, mouse; C493975:Cdkn2d protein, mouse; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050764:Cyclin-Dependent Kinase Inhibitor p19; D025803:Tumor Suppressor Protein p14ARF; D025521:Tumor Suppressor Proteins