TI  - Regulation of the <prot>Ets</prot>-related transcription factor  <prot>Elf-1</prot>  by binding to the
       <prot>retinoblastoma</prot> protein .
PG  - 1330-5
AB  - The <prot>retinoblastoma</prot> gene product (<prot>Rb</prot>) is a nuclear phosphoprotein that
      regulates cell cycle progression. <prot>Elf-1</prot> is a lymphoid-specific <prot>Ets</prot>
      transcription factor that regulates inducible gene expression during T
      cell activation. In this report, it is demonstrated that  <prot>Elf-1</prot>  contains a
      sequence motif that is highly related to the <prot>Rb</prot> binding sites of several
      viral oncoproteins and binds to the pocket region of  <prot>Rb</prot>  both in vitro and
      in vivo.  <prot>Elf-1</prot>  binds exclusively to the underphosphorylated form of  <prot>Rb</prot>  and
      fails to bind to <prot>Rb</prot> mutants derived from patients with retinoblastoma.
      Co-immunoprecipitation experiments demonstrated an association between
       <prot>Elf-1</prot>  and  <prot>Rb</prot>  in resting normal human T cells. After T cell activation, the
      phosphorylation of <prot>Rb</prot> results in the release of <prot>Elf-1</prot>, which is correlated
      temporally with the activation of <prot>Elf-1</prot>-mediated transcription.
      Overexpression of a phosphorylation-defective form of <prot>Rb</prot> inhibited
      <prot>Elf-1</prot>-dependent transcription during T cell activation. These results
      demonstrate that  <prot>Rb</prot>  interacts specifically with a lineage-restricted  <prot>Ets</prot>
      transcription factor . This regulated interaction may be important for the
      coordination of lineage-specific effector functions such as lymphokine
      production with cell cycle progression in activated T cells.
AD  - Department of Medicine, University of Chicago, IL 60637.
