Disease relevance of piwi

• Evidence for a piwi-dependent RNA silencing of the gypsy endogenous retrovirus by the Drosophila melanogaster flamenco gene [1].

High impact information on piwi

• Here, we examine piwi-interacting RNAs (piRNAs) associated with each Drosophila Piwi protein and find that Piwi and Aubergine bind RNAs that are predominantly antisense to transposons, whereas Ago3 complexes contain predominantly sense piRNAs [2].
• In Drosophila, Piwi (P-element-induced wimpy testis), which encodes a protein of the Argonaute family, is essential for germ stem cell self-renewal [3].
• These data together imply that Piwi functions in nuclear RNA silencing as Slicer by associating specifically with rasiRNAs originating from repetitive targets [3].
• Specific association of Piwi with rasiRNAs derived from retrotransposon and heterochromatic regions in the Drosophila genome [3].
• However, little is known about the molecular mechanisms of Piwi-dependent gene silencing [3].

Biological context of piwi

• To search for such genes, we screened the Drosophila third chromosome ( approximately 36% of the euchromatic genome) for suppressor mutations of piwi2 and identified six strong and three weak piwi suppressor genes/sequences [4].
• The piwi mutation, which is known to affect RNA-mediated homology-dependent transgene silencing, was also shown to impede the repression of gypsy in restrictive female gonads [1].
• Piwi-associated small RNAs were identified by cloning and sequencing as repeat-associated small interfering RNAs (rasiRNAs) derived from repetitive regions, such as retrotransposon and heterochromatic regions, in the Drosophila genome [3].

Anatomical context of piwi

• Yb modulates the divisions of both germline and somatic stem cells through piwi- and hh-mediated mechanisms in the Drosophila ovary [5].
• Despite numerous studies, it is not clear what roles piwi, primarily a cap cell factor, and pumilio, a germ cell factor, play in maintaining GSC function [6].
• PIWI is a maternal component of the polar granule, a germ-plasm-specific organelle essential for germline specification [7].

Associations of piwi with chemical compounds

• Aub- and Piwi-associated rasiRNAs showed a strong preference for uracil at their 5' ends, and AGO3-associated rasiRNAs showed a strong preference for adenine at nucleotide 10 [8].

Other interactions of piwi

• Regulatory relationship among piwi, pumilio, and bag-of-marbles in Drosophila germline stem cell self-renewal and differentiation [9].
• With molecular and genetic experiments, we show that piwi maintains GSCs by silencing bam [6].
• The piwi gene encoding protein of the Drosophila Argonaute family was shown to be required for the germ stem cells maintenance [10].
• Ziwi, the zebrafish homologue of the Drosophila piwi: co-localization with vasa at the embryonic genital ridge and gonad-specific expression in the adults [11].
• Polycomb, pairing and PIWI - RNA silencing and nuclear interactions [12].

Analytical, diagnostic and therapeutic context of piwi

• We applied inverse PCR approach to detect the newly arisen insertions of the mdg1 retrotransposon in the progeny of individual piwi mutant males [10].
• Northern blot analyses revealed that in vivo Piwi does not associate with microRNAs (miRNAs) and that guide siRNA was not loaded onto Piwi when siRNA duplex was added to ovary lysate [3].

References