TI  -  <prot>14-3-3  zeta</prot> negatively regulates  <prot>raf-1</prot>  activity by interactions with the
      <prot>Raf-1</prot> cysteine-rich domain.
PG  - 20990-3
AB  - Although <prot>Raf-1</prot> is a critical effector of <prot>Ras</prot> signaling and transformation,
      the mechanism by which <prot>Ras</prot> promotes <prot>Raf-1</prot> activation is complex and
      remains poorly understood. We recently reported that  <prot>Ras</prot>  interaction with
      the  <prot><prot>Raf-1</prot>  cysteine-rich domain</prot> (<prot>Raf-CRD</prot>, residues 139-184) may be required
      for <prot>Raf-1</prot> activation. The <prot>Raf-CRD</prot> is located in the NH2-terminal negative
      regulatory domain of <prot>Raf-1</prot> and is highly homologous to cysteine-rich
      domains found in protein kinase C family members. Recent studies indicate
      that the structural integrity of the <prot>Raf-CRD</prot> is also critical for  <prot>Raf-1</prot> 
      interaction with  14-3-3  proteins. However, whether 14-3-3 proteins
      interact directly with the <prot>Raf-CRD</prot> and how this interaction may mediate
      <prot>Raf-1</prot> function has not been determined. In the present study, we
      demonstrate that  <prot>14-3-3 zeta</prot>  binds directly to the isolated  <prot>Raf-CRD</prot> .
      Moreover, mutation of <prot>Raf-1</prot> residues 143-145 impairs binding of  14-3-3 ,
      but not <prot>Ras</prot>, to the  <prot>Raf-CRD</prot> . Introduction of mutations that impair 14-3-3
      binding resulted in full-length <prot>Raf-1</prot> mutants with enhanced transforming
      activity. Thus,  14-3-3  interaction with the  <prot>Raf-CRD</prot>  may serve in negative
      regulation of <prot>Raf-1</prot> function by facilitating dissociation of 14-3-3 from
      the NH2 terminus of <prot>Raf-1</prot> to promote subsequent events necessary for full
      activation of <prot>Raf-1</prot>.
AD  - Department of Pharmacology, Lineberger Comprehensive Cancer Center,
