TI  - A cellular protein that competes with <prot>SV40 T antigen</prot> for binding to the
      <prot>retinoblastoma</prot> gene product.
PG  - 160-2
AB  - Tumour-suppressor genes, such as the human <prot>retinoblastoma susceptibility
      gene</prot> (<prot>Rb</prot>), are widely recognized as being vital in the control of cell
      growth and tumour formation. This role is indicated, in part, by the
      suppression of tumorigenicity of human tumour cells after
      retrovirus-mediated <prot>Rb</prot> replacement. How <prot>Rb</prot> acts to bring about this
      suppression is not clear but one clue is that the <prot>Rb</prot> protein forms
      complexes with the transforming oncoproteins of several DNA tumour
      viruses, and that two regions of <prot>Rb</prot> essential for such binding frequently
      contain mutations in tumour cells. These observations suggest that
      endogenous cellular proteins might exist that bind to the same regions of
      <prot>Rb</prot> and thereby mediate its function. We report here the identification of
      one such human cellular <prot><prot>Rb</prot>-associated protein</prot> of relative molecular mass
      46,000 (46K) (<prot>RbAP46</prot>). Two lines of evidence support the notion that
       <prot>RbAP46</prot>  and <prot>simian virus 40 T antigen</prot> have homologous  <prot>Rb</prot> -binding
      properties: first, several mutated <prot>Rb</prot> proteins that failed to bind to T
      also did not associate with <prot>RbAP46</prot>; and second, both T antigen and T
      peptide (amino acids 101-118) were able to compete with  <prot>RbAP46</prot>  for binding
      to  <prot>Rb</prot> . The apparent targeting of the  <prot>RbAP46</prot> - <prot>Rb</prot>  interaction by oncoproteins
      of DNA tumour viruses strongly suggests that formation of this complex is
      functionally important.
AD  - Department of Pathology, School of Medicine, University of California, San
