TI  - The <prot>retinoblastoma protein</prot> associates with the <prot>protein phosphatase type 1</prot>
      catalytic subunit.
PG  - 555-69
AB  - The <prot>retinoblastoma protein</prot> (<prot>p110RB</prot>) interacts with many cellular proteins
      in complexes potentially important for its growth-suppressing function. We
      have developed and used an improved version of the yeast two-hybrid system
      to isolate human cDNAs encoding proteins able to bind  <prot>p110RB</prot> . One clone
      encodes a novel  <prot>type 1 protein phosphatase</prot> catalytic subunit (<prot>PP-1 alpha
      2</prot>) , which differs from the originally defined <prot>PP-1 alpha</prot> by an
      amino-terminal 11-amino-acid insert. In vitro-binding assays demonstrated
      that  <prot>PP-1 alpha</prot>  isoforms preferentially bind the hypophosphorylated form
      of  <prot>p110RB</prot> . Moreover, similar  <prot>p110RB</prot>  sequences are required for binding
       <prot>PP-1 alpha 2</prot> and <prot>SV40 large T antigen</prot>. Cell cycle synchrony experiments
      revealed that this association occurs from mitosis to early G1. The
      implications of these findings on the regulation of both proteins are
      discussed.
AD  - Center for Molecular Medicine/Institute of Biotechnology, University of
