title: Direct evidence of nuclear Argonaute distribution during transcriptional silencing links the actin cytoskeleton to nuclear RNAi machinery in human cells.
abstract: Mammalian RNAi machinery facilitating transcriptional gene silencing (TGS) is the RNA-induced transcriptional gene silencing-like (RITS-like) complex, comprising of Argonaute (Ago) and small interfering RNA (siRNA) components. We have previously demonstrated promoter-targeted siRNA induce TGS in human immunodeficiency virus type-1 (HIV-1) and simian immunodeficiency virus (SIV), which profoundly suppresses retrovirus replication via heterochromatin formation and histone methylation. Here, we examine subcellular co-localization of Ago proteins with promoter-targeted siRNAs during TGS of SIV and HIV-1 infection. Analysis of retrovirus-infected cells revealed Ago1 co-localized with siRNA in the nucleus, while Ago2 co-localized with siRNA in the inner nuclear envelope. Mismatched and scrambled siRNAs were observed in the cytoplasm, indicating sequence specificity. This is the first report directly visualizing nuclear compartment distribution of Ago-associated siRNA and further reveals a novel nuclear trafficking mechanism for RITS-like components involving the actin cytoskeleton. These results establish a model for elucidating mammalian TGS and suggest a fundamental mechanism underlying nuclear delivery of RITS-like components.
authors: St Vincent's Centre for Applied Medical Research, Darlinghurst, Australia. c.hood@amr.org.au
authors: Chantelle L
authors: CL
authors: Ahlenstiel
authors: Heidi G W
authors: HG
authors: Lim
authors: David A
authors: DA
authors: Cooper
authors: Takaomi
authors: T
authors: Ishida
authors: Anthony D
authors: AD
authors: Kelleher
authors: Kazuo
authors: K
authors: Suzuki
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D060565:Argonaute Proteins / Q000032:analysis* / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D039642:Eukaryotic Initiation Factors / Q000032:analysis / Q000378:metabolism; D020868:Gene Silencing; D015497:HIV-1 / Q000502:physiology; D006801:Humans; D009685:Nuclear Envelope / Q000737:chemistry; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000032:analysis*; D015302:Simian Immunodeficiency Virus / Q000502:physiology; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: C115848:AGO1 protein, human; C466422:AGO2 protein, human; D000199:Actins; D060565:Argonaute Proteins; D039642:Eukaryotic Initiation Factors; D034741:RNA, Small Interfering; D015638:Cytochalasin D