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Typus
Verschleierung
Bearbeiter
SleepyHollow02
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Untersuchte Arbeit:
Seite: 12, Zeilen: 1-20
Quelle: Hammond 2005
Seite(n): 5825 f., Zeilen: 5825: r.col. last lines; 5826: l.co. 1 ff., 26 ff.
Structurally, this protein family is characterized by two domains, the PAZ domain and the PIWI domain. Structures for both domains have been solved. Additional RISC components with unknown roles in RNAi have also been identified. These include the RNA binding protein VIG, the Drosophila homolog of the Fragile X protein, dFXR, helicase proteins, and Tudor-SN (Ishizuka et al, 2002; Caudy et al, 2003). This last protein has five staphylococcal nuclease (SNase) domains and a Tudor domain. In humans, there are four closely related Argonaute family members, named Ago1-4. All four bind siRNAs and miRNAs at similar levels, and are widely expressed. Only Ago2, however, is present in a cleavage-competent RISC-complex (Meister et al, 2004). Similarly, siRNA-mediated knockdown, or targeted knockout, of Ago2 impaired RNAi of a reporter, while knockdown of Ago1, 3, 4 had no effect. The crystal structure of an Argonaute family member from Pyrococcus furiosus has been revealed (Song et al, 2004). The structure displayed an RNaseH fold for the signature PIWI domain. The crystal structure of a second archaean argonaute, Archaeoglobus fulgidus Piwi (AfPiwi), confirmed the RNaseH fold (Parker et al, 2004). The final demonstration that Slicer activity was contained within Ago2 was the reconstitution of minimal RISC with bacterially expressed, purified Ago2 and a single-stranded siRNA (Rivas et al, 2005). Structurally, this protein family is characterized by two domains, the PAZ domain and the PIWI domain. Structures for both domains have been solved (see below). Additional RISC components with unknown roles in RNAi

[5826:]

have also been identified. These include the RNA binding protein VIG, the Drosophila homolog of the Fragile X protein, dFXR, helicase proteins, and Tudor-SN [46–48]. This last protein has five staphylococcal nuclease (SNase) domains and a Tudor domain. [...]

[...]

[...] In humans, there are four closely related Argonaute family members, named Ago1-4. All four bind siRNAs and microRNAs at similar levels, and are widely expressed. Only Ago2, however, is present in a cleavage- competent RISC [52,53]. Similarly, siRNA-mediated knockdown, or targeted knockout, of Ago2 impairs RNAi of a reporter, while knockdown of Ago1, 3, 4 had no effect. These data can be interpreted in two ways: Ago2 alone is capable of interacting with Slicer, or Ago2 itself is Slicer. The answer was provided by the crystal structure of an Argonaute family member from Pyrococcus furiosus [54]. The structure revealed an RNaseH fold for the signature PIWI domain. The crystal structure of a second archaean Argonaute, Archaeoglobus fulgidus Piwi (AfPiwi), confirmed the RNaseH fold [55]. The final demonstration that Slicer activity was contained within Ago2 was the reconstitution of minimal RISC with bacterially expressed, purified Ago2 and a single-stranded siRNA [45].


[46] Caudy, A.A., Myers, M., Hannon, G.J. and Hammond, S.M. (2002) Fragile X-related protein and VIG associate with the RNA interference machinery. Genes Dev. 16, 2491–2496.

[47] Caudy, A.A. et al. (2003) A micrococcal nuclease homologue in RNAi effector complexes. Nature 425, 411–414.

[48] Ishizuka, A., Siomi, M.C. and Siomi, H. (2002) A Drosophila fragile X protein interacts with components of RNAi and ribosomal proteins. Genes Dev. 16, 2497–2508.

[52] Meister, G., Landthaler, M., Patkaniowska, A., Dorsett, Y., Teng, G. and Tuschl, T. (2004) Human Argonaute2 mediates RNA cleavage targeted by miRNAs and siRNAs. Mol. Cell 15, 185–197.

[53] Liu, J. et al. (2004) Argonaute2 is the catalytic engine of mammalian RNAi. Science 305, 1437–1441.

[54] Song, J.J., Smith, S.K., Hannon, G.J. and Joshua-Tor, L. (2004) Crystal structure of Argonaute and its implications for RISC slicer activity. Science 305, 1434–1437.

[55] Parker, J.S., Roe, S.M. and Barford, D. (2004) Crystal structure of a PIWI protein suggests mechanisms for siRNA recognition and slicer activity. EMBO J. 23, 4727–4737.

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