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* IRF family signature *
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Viral infections induce  the  expression  of type I interferons (IFN-alpha and
IFN-beta) genes. The induction is due to the transcriptional activation of the
IFN genes.  Interferon regulatory factor I (IRF-1) is one of the transcription
factors responsible for that activation. IRF-1 binds to an upstream regulatory
cis element, known as the interferon consensus sequence (ICS),  which is found
in the promoters of type I IFN and IFN-inducible MHC class I genes. Interferon
regulatory factor 2 (IRF-2) is a protein that also interacts with the ICS, but
that does not function as an activator;  rather, it suppresses the function of
IRF-1 under certain circumstances [1].

The IRF proteins share a highly conserved  N-terminal domain of 114 amino acid
residues which is probably involved in DNA-binding  and  which is also present
in the following proteins:

 - Interferon consensus sequence binding protein (ICSBP) [2],  a transcription
   factor expressed predominantly in lymphoid tissues and induced by IFN-gamma
   that also binds to the ICS.
 - Transcriptional regulator ISGF3 gamma subunit [3]. ISGF3 is responsible for
   the initial stimulation of interferon-alpha-responsive genes. It recognizes
   and binds to  the interferon-stimulated  response element (ISRE) within the
   regulatory sequences of target genes.

These proteins share a  highly  conserved  N-terminal domain of 114 amino acid
residues which is probably involved in DNA-binding.  As  a  signature for this
family of proteins we selected a  conserved region in position 74 to 96 of the
domain.

-Consensus pattern: P-x(2)-W-K-[TA]-x(2)-R-C-A-[LIVM]-N-x(6)-E-V-x-[DE]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.
-Last update: October 1993 / Pattern and text revised.

[ 1] Taniguchi T.
     J. Interferon Res. 9:633-640(1989).
[ 2] Driggers P.H., Ennist D.L., Gleason S.L., Mak W.-H., Marks M.S.,
     Levi B.-Z., Flanagan J.R., Appella E., Ozato K.
     Proc. Natl. Acad. Sci. U.S.A. 87:3743-3747(1990).
[ 3] Veals S.A., Schindler C., Leonard D., Fu X.-Y., Aebersold R.,
     Darnell J.E. Jr., Levy D.E.
     Mol. Cell. Biol. 12:3315-3324(1992).