Structural highlights
Function
[PA_INCJH] Implicated in endonuclease cleavage of capped RNA primers. Displays an elongation factor activity in viral RNA synthesis. Dispensable for viral transcription, but not replication (By similarity). [PB2_INCJH] Involved in transcription initiation and cap-stealing mechanism, in which cellular capped pre-mRNA are used to generate primers for viral transcription. Binds the cap of the target pre-RNA which is subsequently cleaved by PB1 (By similarity). [RDRP_INCJH] RNA-dependent RNA polymerase which is responsible for replication and transcription of virus segments. Binds the promoter sequence of the encapsidated viral RNA. Displays an endonuclease activity involved in cap-stealing. Cleaves cellular pre-mRNA to generate primers for viral transcription (By similarity).
Publication Abstract from PubMed
Negative-sense RNA viruses, such as influenza, encode large, multidomain RNA-dependent RNA polymerases that can both transcribe and replicate the viral RNA genome. In influenza virus, the polymerase (FluPol) is composed of three polypeptides: PB1, PB2 and PA/P3. PB1 houses the polymerase active site, whereas PB2 and PA/P3 contain, respectively, cap-binding and endonuclease domains required for transcription initiation by cap-snatching. Replication occurs through de novo initiation and involves a complementary RNA intermediate. Currently available structures of the influenza A and B virus polymerases include promoter RNA (the 5' and 3' termini of viral genome segments), showing FluPol in transcription pre-initiation states. Here we report the structure of apo-FluPol from an influenza C virus, solved by X-ray crystallography to 3.9 A, revealing a new 'closed' conformation. The apo-FluPol forms a compact particle with PB1 at its centre, capped on one face by PB2 and clamped between the two globular domains of P3. Notably, this structure is radically different from those of promoter-bound FluPols. The endonuclease domain of P3 and the domains within the carboxy-terminal two-thirds of PB2 are completely rearranged. The cap-binding site is occluded by PB2, resulting in a conformation that is incompatible with transcription initiation. Thus, our structure captures FluPol in a closed, transcription pre-activation state. This reveals the conformation of newly made apo-FluPol in an infected cell, but may also apply to FluPol in the context of a non-transcribing ribonucleoprotein complex. Comparison of the apo-FluPol structure with those of promoter-bound FluPols allows us to propose a mechanism for FluPol activation. Our study demonstrates the remarkable flexibility of influenza virus RNA polymerase, and aids our understanding of the mechanisms controlling transcription and genome replication.
Crystal structure of the RNA-dependent RNA polymerase from influenza C virus.,Hengrung N, El Omari K, Serna Martin I, Vreede FT, Cusack S, Rambo RP, Vonrhein C, Bricogne G, Stuart DI, Grimes JM, Fodor E Nature. 2015 Nov 5;527(7576):114-7. doi: 10.1038/nature15525. Epub 2015 Oct 26. PMID:26503046[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Hengrung N, El Omari K, Serna Martin I, Vreede FT, Cusack S, Rambo RP, Vonrhein C, Bricogne G, Stuart DI, Grimes JM, Fodor E. Crystal structure of the RNA-dependent RNA polymerase from influenza C virus. Nature. 2015 Nov 5;527(7576):114-7. doi: 10.1038/nature15525. Epub 2015 Oct 26. PMID:26503046 doi:http://dx.doi.org/10.1038/nature15525
