title: Membrane association of polyomavirus middle-T antigen in an in vitro system.
abstract: Polyomavirus-infected cells express three proteins in the early phase of the lytic cycle, the so-called tumor antigens. Two of them, large- and middle-T antigens, are also required for virus-mediated transformation of primary cells, while middle-T alone is sufficient to transform established cells in culture. Cell transformation by middle-T is strictly dependent on the ability of this protein to associate with cellular enzymes like members of the Src family of tyrosine kinases, a phosphatidylinositol 3-kinase, phosphatase 2A and SHC, an adapter protein linking GDP/GTP exchange factors to tyrosine kinase receptors. A carboxy-terminal stretch of 22 hydrophobic amino acids is required for targeting middle-T and associated proteins to cellular membranes. Here we show in an in vitro system that middle-T fusion proteins carrying an amino-terminal hemagglutinin leader sequence are capable to bind to and enter the lumen of dog pancreas microsomes supporting the concept that the carboxy-terminus of middle-T is an authentic membrane-targeting domain. Furthermore, wild-type middle-T, but not a truncated protein lacking the putative membrane anchor, specifically associates with artificial lipid bilayers.
authors.affiliation: MGH/Harvard Cutaneous Biology Research Center, MGH-East, Charlestown, MA 02129, USA.
authors.forename: U
authors.initials: U
authors.lastname: Hofer
authors.forename: B
authors.initials: B
authors.lastname: Wehrle
authors.forename: K
authors.initials: K
authors.lastname: Ballmer-Hofer
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology*; D004285:Dogs; D006389:Hemagglutinins, Viral / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D008081:Liposomes / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D010179:Pancreas / Q000166:cytology / Q000378:metabolism / Q000821:virology*; D010713:Phosphatidylcholines / Q000378:metabolism; D011120:Polyomavirus / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D000952:Antigens, Polyomavirus Transforming; D006389:Hemagglutinins, Viral; D008081:Liposomes; D010713:Phosphatidylcholines; D011993:Recombinant Fusion Proteins