title: Pokeweed antiviral protein alters splicing of HIV-1 RNAs, resulting in reduced virus production.
abstract: Processing of HIV-1 transcripts results in three populations in the cytoplasm of infected cells: full-length RNA, singly spliced, and multiply spliced RNAs. Rev, regulator of virion expression, is an essential regulatory protein of HIV-1 required for transporting unspliced and singly spliced viral transcripts from the nucleus to the cytoplasm. Export allows these RNAs to be translated and the full-length RNA to be packaged into virus particles. In our study, we investigate the activity of pokeweed antiviral protein (PAP), a glycosidase isolated from the pokeweed plant Phytolacca americana, on the processing of viral RNAs. We show that coexpression of PAP with a proviral clone alters the splicing ratio of HIV-1 RNAs. Specifically, PAP causes the accumulation of multiply spliced 2-kb RNAs at the expense of full-length 9-kb and singly spliced 4-kb RNAs. The change in splicing ratio is due to a decrease in activity of Rev. We show that PAP depurinates the rev open reading frame and that this damage to the viral RNA inhibits its translation. By decreasing Rev expression, PAP indirectly reduces the availability of full-length 9-kb RNA for packaging and translation of the encoded structural proteins required for synthesis of viral particles. The decline we observe in virus protein expression is not due to cellular toxicity as PAP did not diminish translation rate. Our results describing the reduced activity of a regulatory protein of HIV-1, with resulting change in virus mRNA ratios, provides new insight into the antiviral mechanism of PAP.
authors.affiliation: Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Alice
authors.initials: A
authors.lastname: Zhabokritsky
authors.affiliation: Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Sheila
authors.initials: S
authors.lastname: Mansouri
authors.affiliation: Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Katalin A
authors.initials: KA
authors.lastname: Hudak
mesh_terms: D001692:Biological Transport; D002460:Cell Line; D015870:Gene Expression; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D016366:Open Reading Frames; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics* / Q000378:metabolism*; D054789:Ribosome Inactivating Proteins, Type 1 / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics; D014779:Virus Replication; D054321:rev Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D054789:Ribosome Inactivating Proteins, Type 1; D014764:Viral Proteins; D054321:rev Gene Products, Human Immunodeficiency Virus; C024275:pokeweed antiviral protein
keywords: HIV-1; Rev; glycosidase; pokeweed antiviral protein; ribosome inactivating protein