The cellular proteins which can associate specifically with polyomavirus middle T antigen in human 293 cells include the major human 70-kilodalton heat shock proteins

Abstract

We compared the proteins which associate with middle T antigen (MT) of polyomavirus in human cells infected with Ad5(pymT), a recombinant adenovirus which directs the overexpression of MT, with the MT-associated proteins (MTAPs) previously identified in murine fibroblasts expressing MT. MTAPs of 27, 29, 36, and 63 kilodaltons (kDa) appeared to be fairly well conserved between the two species, as judged by comigration on two-dimensional gels. Several 61-kDa MTAP species detected in MT immunoprecipitates from both cell sources also comigrated on these gels. However, no protein comigrating precisely with the murine 85-kDa MTAP could be detected in the human cells. Furthermore, two proteins of 72 and 74 kDa associated with wild-type MT in the infected human cells but not in murine fibroblasts expressing MT. It had been previously reported for murine cells that the 70-kDa heat shock protein associates with a particular mutant MT but not with wild-type MT (G. Walter, A. Carbone, and W. J. Welch, J. Virol. 61:405-410, 1987). By the criteria of comigration on two-dimensional gels, tryptic peptide mapping, and immunoblotting, we showed that the 72-and 74-kDa proteins that associate with wild-type MT in human cells are the major human 70-kDa heat shock proteins.

Identification of regions in polyomavirus middle T and small t antigens important for association with protein phosphatase 2A

“…Alternatively, the availability of a heat shock protein binding site may be exposed when other MT-associated proteins are not bound to MT (36). Consistent with the latter possibility, wild-type MT associates with the 73K heat shock protein when MT levels are in excess of PP2A levels (36). In addition, we have preliminary evidence to indicate the existence of a specific binding site on MT for the 73K heat shock protein (unpublished data).…”

“…It is possible that this binding is due to improper folding of the mutant proteins. Alternatively, the availability of a heat shock protein binding site may be exposed when other MT-associated proteins are not bound to MT (36). Consistent with the latter possibility, wild-type MT associates with the 73K heat shock protein when MT levels are in excess of PP2A levels (36).…”

“…In each case, the level of the 85-kDa protein varied in parallel with the presumed pp60 c-src band. Finally, the amount of a 70-kDa protein, 73K heat shock protein (36,55), increased as levels of the other bound proteins decreased.…”

HSC70 interactions with SV40 viral proteins differ between permissive and nonpermissive mammalian cells

“…The role of hsc70 in the viral life cycle remains controversial. Association of hsc70 with early viral oncoproteins has been reported on numerous occasions (Sawai and Butel 1989;Campbell et al 1997;White et al 1988;Pallas et al 1989;Sheng et al 1997) but the significance of these interactions is still obscure. In the case of SV40 T antigen, binding to cellular hsc70 was reported in transformed cells which do not support viral propagation (Sawai and Butel 1989;Campbell et al 1997).…”

Do Stress Proteins Play a Role in Arthritis and Autoimmunity?

“…Perhaps of more interest is the possibility that stress proteins, such as hsp70 or ubiquitin, may be ingredients in the "immunogenic particle" concept (Tan et al 1988) of the origin of anti-nuclear and other autoantibodies. Thus, hsp70 associates with proteins in the nucleus and nucleolus in a cell cycledependent fashion (Milarski et al 1989), migrates among different cell compartments, and binds to a variety of nuclear and cytoplasmic proteins in virus-infected cells (Welch & Suhan 1986, Welch et al 1985, Sawai & Butel 1989, Pallas et al 1989, La Thangue & Latchman 1988, Nevins 1982, White et al 1988, Jay et al 1978, Opperman et al 1981, Schuh et al 1985, Colhns & Hightower 1982 and in cells exposed to other stressful stimuli. Similarly, ubiquitin forms particles ubiquitously as part of a mechanism for the clearance of denatured proteins.…”