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The PAZ domain is a domain of about 110 amino-acids which has been named after three of the proteins containing it: Piwi, Argonaute and Zwille/Pinhead [1]. It is found in the Argonaute and the Dicer protein families, whose members are implicated in stem-cell fate determination and post-transcriptional gene silencing (PTGS) through RNA interference (RNAi) [2,3]. PTGS RNAi is the mechanism through which double-stranded RNAs (dsRNAs) silence cognate genes. It is characterized by the presence of RNAs of about 22 nucleotides in length that are homologous to the gene to be suppressed. These nucleotide sequences serve as guide sequences that instruct the RNA-induced silencing complex (RISC) nuclease to destroy specific mRNAs [4]. Proteins belonging to the Dicer family are enzymes that are involved in the generation of putative guide RNAs by specifically cleaving dsRNAs [3]. The function of proteins of the Argonaute family is not known, but they could be implicated in transcriptional initiation [2].

Although the sequence of the PAZ domain does not reveal its possible role, its presence in both the Argonaute and Dicer protein families indicates that it might be important for the function of these proteins in RNAi and cell differentiation [1].

Some proteins known to contain a PAZ domain are listed below:

Proteins of the Argonaute family:

• Eukaryotic translation initiation factor 2C (eIF2C). It plays an important role in the eukaryotic peptide chain initiation process.
• Drosophila Piwi proteins. It is essential for germ-line stem cell 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.

These proteins also contain a Piwi domain (see <PDOC50822>) in addition to the PAZ domain [1].

Proteins of the Dicer family:

• Drosophila Dicer (Dcr) protein.
• Arabidopsis thaliana Carpel Factory (CAF) protein. It is homologous to Dcr and plays a role in floral meristem determinacy [5].

In addition to the PAZ domain, these proteins contain DEAD/DEAH box helicase (see <PDOC00039>), RNase III (see <PDOC00448>) and double stranded RNA-binding domains (dsRBD) (see <PDOC50137>).

The profile we have developed covers the entire PAZ domain.

May 2002 / First entry.

PROSITE method (with tools and information) covered by this documentation:

PAZ, PS50821; PAZ 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 PS50821 • 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 PS50821 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS50821 • Scan Swiss-Prot/TrEMBL entries against PS50821 • view ligand binding statistics

Matching PDB structures: 1R6Z 1SI2 1SI3 1T2R ... [ALL]

1	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

2	Authors	Fagard M., Boutet S., Morel J.-B., Bellini C., Vaucheret H.
	Title	AGO1, QDE-2, and RDE-1 are related proteins required for post-transcriptional gene silencing in plants, quelling in fungi, and RNA interference in animals.
	Source	Proc. Natl. Acad. Sci. U.S.A. 97:11650-11654(2000).
	PubMed ID	11016954
	DOI	10.1073/pnas.200217597

3	Authors	Bernstein E., Caudy A.A., Hammond S.M., Hannon G.J.
	Title	Role for a bidentate ribonuclease in the initiation step of RNA interference.
	Source	Nature 409:363-366(2001).
	PubMed ID	11201747
	DOI	10.1038/35053110

4	Authors	Hammond S.M., Caudy A.A., Hannon G.J.
	Title	Post-transcriptional gene silencing by double-stranded RNA.
	Source	Nat. Rev. Genet. 2:110-119(2001).
	PubMed ID	11253050
	DOI	10.1038/35052556

5	Authors	Jacobsen S.E., Running M.P., Meyerowitz E.M.
	Title	Disruption of an RNA helicase/RNAse III gene in Arabidopsis causes unregulated cell division in floral meristems.
	Source	Development 126:5231-5243(1999).
	PubMed ID	10556049

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