4o42
From Proteopedia
Tandem chromodomains of human CHD1 in complex with influenza NS1 C-terminal tail dimethylated at K229
Structural highlights
Function[CHD1_HUMAN] ATP-dependent chromatin-remodeling factor which functions as substrate recognition component of the transcription regulatory histone acetylation (HAT) complex SAGA. Regulates polymerase II transcription. Also required for efficient transcription by RNA polymerase I, and more specifically the polymerase I transcription termination step. Regulates negatively DNA replication. Not only involved in transcription-related chromatin-remodeling, but also required to maintain a specific chromatin configuration across the genome. Is also associated with histone deacetylase (HDAC) activity (By similarity). Required for the bridging of SNF2, the FACT complex, the PAF complex as well as the U2 snRNP complex to H3K4me3. Functions to modulate the efficiency of pre-mRNA splicing in part through physical bridging of spliceosomal components to H3K4me3. Required for maintaining open chromatin and pluripotency in embryonic stem cells.[1] [NS1_I83A8] Inhibits post-transcriptional processing of cellular pre-mRNA, by binding and inhibiting two cellular proteins that are required for the 3'-end processing of cellular pre-mRNAs: the 30 kDa cleavage and polyadenylation specificity factor (CPSF4) and the poly(A)-binding protein 2 (PABPN1). This results in the accumulation of unprocessed 3' end pre-mRNAs which can't be exported from the nucleus. Cellular protein synthesis is thereby shut off very early after virus infection. Viral protein synthesis is not affected by the inhibition of the cellular 3' end processing machinery because the poly(A) tails of viral mRNAs are produced by the viral polymerase through a stuttering mechanism (By similarity). Prevents the establishment of the cellular antiviral state by inhibiting TRIM25-mediated DDX58 ubiquitination, which normally triggers the antiviral transduction signal that leads to the activation of type I IFN genes by transcription factors like IRF3 and IRF7. Prevents human EIF2AK2/PKR activation, either by binding double-strand RNA, or by interacting directly with EIF2AK2/PKR. This function may be important at the very beginning of the infection, when NS1 is mainly present in the cytoplasm. Also binds poly(A) and U6 snRNA. Suppresses the RNA silencing-based antiviral response in Drosophila cells (By similarity). Publication Abstract from PubMedPathogens can interfere with vital biological processes of their host by mimicking host proteins. The NS1 protein of the influenza A H3N2 subtype possesses a histone H3K4-like sequence at its carboxyl terminus and has been reported to use this mimic to hijack host proteins. However, this mimic lacks a free N-terminus that is essential for binding to many known H3K4 readers. Here we show that the double chromodomains of CHD1 adopt an 'open pocket' to interact with the free N-terminal amine of H3K4, and the open pocket permits the NS1 mimic to bind in a distinct conformation. We also explored the possibility that NS1 hijacks other cellular proteins and found that the NS1 mimic has access to only a subset of chromatin-associated factors, such as WDR5. Moreover, methylation of the NS1 mimic can not be reversed by the H3K4 demethylase LSD1. Overall, we thus conclude that the NS1 mimic is an imperfect histone mimic. Structural basis for histone mimicry and hijacking of host proteins by influenza virus protein NS1.,Qin S, Liu Y, Tempel W, Eram MS, Bian C, Liu K, Senisterra G, Crombet L, Vedadi M, Min J Nat Commun. 2014 May 23;5:3952. doi: 10.1038/ncomms4952. PMID:24853335[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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