TI  - Multiple proteins physically interact with  <prot>PU.1</prot> . Transcriptional synergy
      with  <prot>NF-IL6 beta</prot>  (C/<prot>EBP delta</prot>, <prot>CRP3</prot>).
PG  - 4330-8
AB  - <prot>PU.1</prot> is a transcription factor that belongs to the ets family of DNA
      binding proteins. In this study, we show by Far Western blot analyses that
      multiple nuclear proteins are capable of physically interacting with <prot>PU.1</prot>.
      Using radiolabeled <prot>PU.1</prot> protein as a probe, we screened a B cell cDNA
      expression library and isolated a number of clones encoding <prot>PU.1</prot>
      interacting proteins. Three of these clones encode DNA binding proteins
      (<prot>NF-IL6 beta</prot>, <prot>HMG I/Y</prot>, and <prot>SSRP</prot>), one clone encodes a chaperone protein,
      and another clone encodes a multifunctional phosphatase. We have
      characterized the physical and functional interactions between  <prot>PU.1</prot>  and
       <prot>NF-IL6 beta</prot> , a leucine zipper transcription factor implicated in
      inflammatory responses. We found that deletion of the carboxyl-terminal 28
      amino acids of <prot>PU.1</prot> disrupted  <prot>PU.1</prot> - <prot>NF-IL6 beta</prot>  physical interaction. This
      deletion disrupts the <prot>PU.1</prot> Ets domain. Deletion of the <prot>NF-IL6 beta</prot> leucine
      zipper domain also greatly diminished the interaction between these two
      proteins. In transient expression assays, we found that  <prot>PU.1</prot>  and  <prot>NF-IL6 
      beta</prot> can functionally cooperate to synergistically activate transcription.
      Electrophoretic mobility shift assays showed that <prot>PU.1</prot> and <prot>NF-IL6 beta</prot> can
      simultaneously bind to adjacent DNA binding sites, but apparently do not
      influence the kinetics or affinity of each other's DNA binding. These
      results suggest that transcriptional synergy is due to each protein
      independently influencing the basal transcription complex.
AD  - Department of Animal Biology, School of Veterinary Medicine, University of
