title: HTLV-I p30 inhibits multiple S phase entry checkpoints, decreases cyclin E-CDK2 interactions and delays cell cycle progression.
abstract: BACKGROUND
  Human T-cell leukemia virus type I (HTLV-I) has efficiently adapted to its host and establishes a persistent infection characterized by low levels of viral gene expression and slow proliferation of HTLV-I infected cells over decades. We have previously found that HTLV-I p30 is a negative regulator of virus expression.
  
  
  RESULTS
  In this study we show that p30 targets multiple cell cycle checkpoints resulting in a delayed entry into S phase. We found that p30 binds to cyclin E and CDK2 and prevents the formation of active cyclin E-CDK2 complexes. In turn, this decreases the phosphorylation levels of Rb and prevents the release of E2F and its transcriptional activation of genes required for G1/S transition. Our studies also show that HTLV-II p28 does not bind cyclin E and does not affect cell cycle progression.
  
  
  CONCLUSIONS
  In contrast to HTLV-I, the HTLV-II-related retrovirus is not oncogenic in humans. Here we report that the HTLV-I p30 delays cell cycle progression while its homologue, HTLV-II p28, does not, providing evidence for important differences between these two related retrovirus proteins.
authors.affiliation: University of Kansas Medical Center, Department of Pathology and Laboratory Medicine, Kansas City, KS 66160, USA.
authors.forename: Hicham H
authors.initials: HH
authors.lastname: Baydoun
authors.forename: Joanna
authors.initials: J
authors.lastname: Pancewicz
authors.forename: Xuetao
authors.initials: X
authors.lastname: Bai
authors.forename: Christophe
authors.initials: C
authors.lastname: Nicot
mesh_terms: D015153:Blotting, Western; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D006367:HeLa Cells; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D012191:Retroviridae Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000235:genetics / Q000502:physiology*
chemical_list: D019927:Cyclin E; D012191:Retroviridae Proteins; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2