{PDOC50119}
{PS50119; ZF_BBOX}
{BEGIN}
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* Zinc finger B-box-type profile *
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The B-box zinc finger is an around 40 amino acids domain. One or two copies of
this motif are generally associated with a RING finger and a coiled coil motif
to form   the   so-called   tripartite  motif.  It  is  found  essentially  in
transcription factors,   ribonucleoproteins   and proto-oncoproteins,  but  no
function is  clearly  assigned  to  this  domain  [1]. It has been shown to be
essential but not sufficient to localize the PML protein in a punctate pattern
in interphase nuclei [2].

Among  the  7  possible ligands for the zinc atom contained in a B-box, only 4
are  used  and  bind one zinc atom in a Cys2-His2 tetrahedral arrangement. The
NMR  analysis reveals that the B-box structure comprises two beta-strands, two
helical  turns  and  three extended loop regions different from any other zinc
binding motif [3].

Proteins  currently  known  to include the zinc finger B-box domain are listed
below:

 - Mammalian ARD1 protein. GTP-binding protein.
 - Mammalian  PML,  probable transcription factor. Involved in a form of acute
   promyelocytic leukemia (APL).
 - Mammalian  TIF1, transcription intermediary factor 1. Interacts selectively
   in vitro with the AF2-activating domain of the estrogen receptors.
 - Mammalian  RFP,  ret  finger  Protein.  May  function  in  male  germ  cell
   development.
 - Human 52 Kd RO/SS-A protein. A protein of unknown function from the RO/SS-A
   ribonucleoprotein complex.
 - Human HT2A may play a significant role in mediating the biological activity
   of the  HIV-1  tat  protein  in  vivo. Binds specifically to the activation
   domain of  HIV-1  tat  and  can  also  interact with the HIV-2 and EIAV tat
   proteins in vivo.
 - Mouse   RPT1,   trans-acting  factor  that  regulates  gene  expression  of
   interleukin 2  receptor  alpha  chain  and  of human immunodeficiency virus
   type 1.
 - PwA33,  associated  with  the  lambrush  chromosome  loops  in  Pleurodeles
   Waltlii, may function as a component of Ribonucleoprotein complexes.
 - Xenopus  laevis  XNF7  (Xenopus  nuclear  factor  7) protein. There are two
   isoformes (XNF7-O    and    XNF7-B)  of this DNA binding protein. The B-box
   domain of XNF7-B was analysed by NMR [3].

We developed a profile that covers the whole domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: December 2001 / First entry.

[ 1] Borden K.L.
     "RING fingers and B-boxes: zinc-binding protein-protein interaction
     domains."
     Biochem. Cell Biol. 76:351-358(1998).
     PubMed=9923704
[ 2] Borden K.L., Lally J.M., Martin S.R., O'Reilly N.J., Solomon E.,
     Freemont P.S.
     "In vivo and in vitro characterization of the B1 and B2 zinc-binding
     domains from the acute promyelocytic leukemia protooncoprotein PML."
     Proc. Natl. Acad. Sci. U.S.A. 93:1601-1606(1996).
     PubMed=8643677
[ 3] Borden K.L., Lally J.M., Martin S.R., O'Reilly N.J., Etkin L.D.,
     Freemont P.S.
     "Novel topology of a zinc-binding domain from a protein involved in
     regulating early Xenopus development."
     EMBO J. 14:5947-5956(1995).
     PubMed=8846787

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