{PDOC51827}
{PS51827; XTBD}
{BEGIN}
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* XRN2-binding (XTBD) domain profile *
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XRN2 is  an  essential  eukaryotic exoribonuclease that processes and degrades
various substrates.  The ~80-residue XRN2-binding domain (XTBD) constitutes an
XRN2-binding module that is employed by different metazoan proteins to link to
XRN2 [1,2]:

 - Caenorhabditis  elegans  Partner of Xrn-Two protein 1, or PAXT-1 for short.
   Plays a  role  in maintenance of steady-state concentration and turnover of
   microRNAs (miRNA)  by  degradation  of  mature  miRNA  in  complex with the
   exoribonuclease XRN-2.
 - Mammalian  CDKN2A-interacting  protein  (CDKN2AIP)  or  Collaborator of ARF
   (CARF). Regulates  DNA damage response in a dose-dependent manner through a
   number of  signaling pathways involved in cell proliferation, apoptosis and
   senescence.
 - Mammalian CDKN2AIP N-terminal-like protein (CDKN2AIPNL).

The XTBD  domain  folds into a globular four-helix bundle (H1-H4) connected by
three loops (L1-L3) (see <PDB:5FIR>). H1-H3 form an antiparallel helical array
and H4 folds back on top of H2 and H3 at an 90° angle. The four-helical bundle
is mainly  stabilized  by  hydrophobic  helix-helix interactions together with
additional polar  interactions  between  side  chains  located  on neighboring
helices. The  four-helix  bundle  of  XTBD  represents  a  structurally unique
arrangement for XRN2 binding [2].

The profile we developed covers the entire XTBD domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: January 2017 / First entry.

[ 1] Miki T.S., Richter H., Rueegger S., Grosshans H.
     "PAXT-1 promotes XRN2 activity by stabilizing it through a conserved
     domain."
     Mol. Cell 53:351-360(2014).
     PubMed=24462208; DOI=10.1016/j.molcel.2014.01.001
[ 2] Richter H., Katic I., Gut H., Grosshans H.
     "Structural basis and function of XRN2 binding by XTB domains."
     Nat. Struct. Mol. Biol. 23:164-171(2016).
     PubMed=26779609; DOI=10.1038/nsmb.3155

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