title: Human T-lymphotropic virus type 1 oncoprotein tax promotes unscheduled degradation of Pds1p/securin and Clb2p/cyclin B1 and causes chromosomal instability.
abstract: Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia. The HTLV-1 transactivator, Tax, is implicated as the viral oncoprotein. Naïve cells expressing Tax for the first time develop severe cell cycle abnormalities that include increased DNA synthesis, mitotic arrest, appearance of convoluted nuclei with decondensed DNA, and formation of multinucleated cells. Here we report that Tax causes a drastic reduction in Pds1p/securin and Clb2p/cyclin B levels in yeast, rodent, and human cells and a loss of cell viability. With a temperature-sensitive mutant of the CDC23 subunit of the anaphase-promoting complex (APC), cdc23(ts); a temperature-sensitive mutant of cdc20; and a cdh1-null mutant, we show that the diminution of Pds1p and Clb2p brought on by Tax is mediated via the Cdc20p-associated anaphase-promoting complex, APC(Cdc20p). This loss of Pds1p/securin and Clb2p/cyclin B1 occurred before cellular entry into mitosis, caused a G(2)/M cell cycle block, and was accompanied by severe chromosome aneuploidy in both Saccharomyces cerevisiae cells and human diploid fibroblasts. Our results support the notion that Tax aberrantly targets and activates APC(Cdc20p), leading to unscheduled degradation of Pds1p/securin and Clb2p/cyclin B1, a delay or failure in mitotic entry and progression, and faulty chromosome transmission. The chromosomal instability resulting from a Tax-induced deficiency in securin and cyclin B1 provides an explanation for the highly aneuploid nature of adult T-cell leukemia cells.
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
authors.forename: Baoying
authors.initials: B
authors.lastname: Liu
authors.forename: Min-Hui
authors.initials: MH
authors.lastname: Liang
authors.forename: Yu-liang
authors.initials: YL
authors.lastname: Kuo
authors.forename: Wei
authors.initials: W
authors.lastname: Liao
authors.forename: Imre
authors.initials: I
authors.lastname: Boros
authors.forename: Tami
authors.initials: T
authors.lastname: Kleinberger
authors.forename: Jan
authors.initials: J
authors.lastname: Blancato
authors.forename: Chou-Zen
authors.initials: CZ
authors.lastname: Giam
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D064173:Anaphase-Promoting Complex-Cyclosome; D000782:Aneuploidy; D000818:Animals; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D002875:Chromosomes / Q000378:metabolism* / Q000648:ultrastructure; D019926:Cyclin B / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D016195:G2 Phase; D016356:Gene Products, tax / Q000235:genetics* / Q000502:physiology*; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007621:Karyotyping; D008164:Luminescent Proteins / Q000378:metabolism; D008677:Metaphase; D008938:Mitosis; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D064249:Securin; D013696:Temperature; D013936:Thymidine / Q000737:chemistry; D013997:Time Factors; D043743:Ubiquitin-Protein Ligase Complexes
chemical_list: D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; C577441:CDC23 protein, S cerevisiae; C093749:CLB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D016356:Gene Products, tax; D008164:Luminescent Proteins; D009687:Nuclear Proteins; C578004:PDS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; D049452:Green Fluorescent Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D011494:Protein Kinases; C102333:histone H1 kinase; D013936:Thymidine