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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 [3]. 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 [3]. 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 [4].
• Drosophila Sting protein. It could repress general or specific transcript processing.
• 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 cycling.
• 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 formation.
• Arabidopsis thaliana Zwille (Zll) or Pinhead (Pnh). It is a developmental protein required for reliable formation of primary and axillary shoot apical meristems.
• 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:

PIWI, PS50822; Piwi domain profile  (MATRIX)

Sequences known to belong to this class detected by the profile: ALL Other sequence(s) detected in Swiss-Prot: NONE

• Domain architecture view of Swiss-Prot proteins matching PS50822 • Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS50822 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS50822 • Scan Swiss-Prot/TrEMBL entries against PS50822 • view ligand binding statistics

Matching PDB structures: 1W9H 1YTU 2BGG 2W42 ... [ALL]

1	Authors	Cox D.N., Chao A., Baker J., Chang L., Qiao D., Lin H.
	Title	A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal.
	Source	Genes Dev. 12:3715-3727(1998).
	PubMed ID	9851978

2	Authors	Schmidt A., Palumbo G., Bozzetti M.P., Tritto P., Pimpinelli S., Schafer U.
	Title	Genetic and molecular characterization of sting, a gene involved in crystal formation and meiotic drive in the male germ line of Drosophila melanogaster.
	Source	Genetics 151:749-760(1999).
	PubMed ID	9927466

3	Authors	Cerutti L., Mian N., Bateman A.
	Title	Domains in gene silencing and cell differentiation proteins: the novel PAZ domain and redefinition of the Piwi domain.
	Source	Trends Biochem. Sci. 25:481-482(2000).
	PubMed ID	11050429

4	Authors	Cox D.N., Chao A., Lin H.
	Title	piwi encodes a nucleoplasmic factor whose activity modulates the number and division rate of germline stem cells.
	Source	Development 127:503-514(2000).
	PubMed ID	10631171

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