SIZ1, SIZ2, and PIAS (protein inhibitor of activated STAT) proteins form a
conserved family defined by an unusual RING-related domain, the Siz/PIAS RING
finger (SP-RING) . While RING fingers coordinate two Zn2+ ions, with a
cross-brace architecture, the SP-RING finger contains only one Zn2+ ion in
site B, which is coordinated in a tetrahedral configuration (see <PDB:3I2D>).
Three of the four amino acid side chains that coordinate the Zn2+ ion at site
A in RING proteins are lacking in Siz/PIAS proteins . Like classical RING
fingers SP-RINGs function as an E3 enzyme but specific for sumoylation (see
<PDOC00449> for more details on the ubiquitination pathway). The SP-RING zinc
finger has the capacity to interact with Ubc9 (the SUMO specific E2 enzyme)
and the substrate and thus can increase the rate of substrate sumoylation
Some proteins known to contain an SP-RING zinc finger are listed below:
Mammalian PIAS proteins (PIAS 1,3,x and y). They bind to STAT transcription
factors and prevent STAT-activated transcription. The mouse PIAS3 protein
has also been called Msx-interacting-zinc finger protein (Miz1) .
Drosophila Su(var)2-10. It is required for proper chromosome structure and
chromosome inheritance .
Yeast SIZ1 and SIZ2. They are required for SUMO attachment to the
cytoskeletal septin proteins.
Pli1, the unique fission yeast member of the SP-RING family. It is involved
in centromeric function.
The profile we developed covers the whole SP-RING-type zinc finger.
The SP-RING-type zinc finger is also known as the MIZ-type zinc finger
October 2009 / Text revised.
PROSITE method (with tools and information) covered by this documentation:
SP-RING for SUMO: new functions bloom for a ubiquitin-like protein.
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