Cloning and analysis of a FoxO transcription factor from Xiphophorus.
Melanoma development in the fish Xiphophorus is determined, at least in part, by overexpression and activation of the Xmrk-2 oncogene, which triggers a variety of signal transduction pathways resulting in altered cell cycle control. We have begun analysing transcription factors which may link Xmrk-2 with regulation of cell proliferation or apoptosis. Towards this end, we have cloned an FKHR (FoxO sub-family) homolog from Xiphophorus maculatus. The isolated clone is a 2.7 kb cDNA encoding a predicted protein of 664 amino acids. The gene, which we have named FoxO5, maps to Xiphophorus Linkage Group XV. The protein product can be categorized within a branch of the FOXO sub-class, which includes: Danio rerio zFKHR (foxo5), Homo sapiens FKHR-L1 (FoxO3a) and Mus musculus FKHR2 (Foxo3). Notably, the Forkhead DNA binding domain, three Akt consensus phosphorylation sites and a carboxy-terminal minimal activation domain are each highly conserved. A mutated FoxO5 protein with disrupted Akt phosphorylation sites inhibits proliferation, but the wild-type protein fails to do so, when exogenously expressed in Xiphophorus cells derived from a melanoma. The same mutated protein predominantly localizes to the nucleus, yet the wild-type protein seldom does. Further characterization of Xiphophorus FoxO5 will contribute to understanding the molecular basis of carcinogenesis in these species.
Rudd
Michael D
MD
Department of Carcinogenesis, The University of Texas M.D. Anderson Cancer Center, Science Park - Research Division, Smithville, TX 78957, USA.
Johnston
Dennis A
DA
Kazianis
Steven
S
Butler
Andrew P
AP
D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003532:Cyprinodontiformes / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D008164:Luminescent Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins