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The Piwi box (or Sting domain) is an about 40 to 80 amino-acid conserved
region, which was first identified in the C-terminal part of Drosophila Piwi
and Sting proteins, and of related proteins from human, Caenorhabditis
elegans, Arabidopsis thaliana, fission yeast and Dictyostelium discoideum [1,2]. It was later recognized that this conserved region is part of a larger
300-amino-acid domain, called Piwi, which is also found in some prokaryotic
proteins of unknown function . The Piwi domain containing proteins are
often involved in stem-cell maintenance and/or post-transcriptional gene
silencing (PTGS) through RNA interference (RNAi), the mechanism through which
double-stranded RNAs (dsRNAs) silence cognate genes . Neither the structure
nor the function of the Piwi domain are known.
Some proteins known to contain a Piwi domain are listed below:
Drosophila Piwi protein. It is a nuclear protein that acts a key regulator
of stem cell division. Its somatic expression modulates the number of
germline stem cells and the rate of their division, while its germline
expression also contributes to promoting stem cell division in a cell-
autonomous manner. The Piwi domain is essential for its function .
Drosophila Sting protein. It could repress general or specific transcript
Human Hiwi (for human Piwi) protein. It might play a role in maintenance of
stem cell quiescence or downregulation of stem cell or progenitor cell
Caenorhabditis elegans Piwi-related proteins 1 and 2 (prg-1 and prg-2).
They are also required for germ-line self-renewal.
Caenorhabditis elegans RNA Interference Deficient 1 (rde-1). It is required
for RNAi and transposon silencing.
Arabidopsis thaliana Argonaute (Ago) protein. It is involved in RNAi as
well as in leaves and floral organs development and axillary meristems
Arabidopsis thaliana Zwille (Zll) or Pinhead (Pnh). It is a developmental
protein required for reliable formation of primary and axillary shoot
Eukaryotic translation initiation factor 2C (eIF2C). It plays an important
role in the eukaryotic peptide chain initiation process.
The profile we have developed covers the entire Piwi domain.
May 2002 / First entry.
PROSITE method (with tools and information) covered by this documentation:
Cox D.N., Chao A., Baker J., Chang L., Qiao D., Lin H.
A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal.
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