title: Expression of Alternatively Spliced Human T-Cell Leukemia Virus Type 1 mRNAs Is Influenced by Mitosis and by a Novel cis-Acting Regulatory Sequence.
abstract: Human T-cell leukemia virus type 1 (HTLV-1) expression depends on the concerted action of Tax, which drives transcription of the viral genome, and Rex, which favors expression of incompletely spliced mRNAs and determines a 2-phase temporal pattern of viral expression. In the present study, we investigated the Rex dependence of the complete set of alternatively spliced HTLV-1 mRNAs. Analyses of cells transfected with Rex-wild-type and Rex-knockout HTLV-1 molecular clones using splice site-specific quantitative reverse transcription (qRT)-PCR revealed that mRNAs encoding the p30Tof, p13, and p12/8 proteins were Rex dependent, while the p21rex mRNA was Rex independent. These findings provide a rational explanation for the intermediate-late temporal pattern of expression of the p30tof, p13, and p12/8 mRNAs described in previous studies. All the Rex-dependent mRNAs contained a 75-nucleotide intronic region that increased the nuclear retention and degradation of a reporter mRNA in the absence of other viral sequences. Selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) analysis revealed that this sequence formed a stable hairpin structure. Cell cycle synchronization experiments indicated that mitosis partially bypasses the requirement for Rex to export Rex-dependent HTLV-1 transcripts. These findings indicate a link between the cycling properties of the host cell and the temporal pattern of viral expression/latency that might influence the ability of the virus to spread and evade the immune system.
  
  
  OBJECTIVE
  HTLV-1 is a complex retrovirus that causes two distinct pathologies termed adult T-cell leukemia/lymphoma and tropical spastic paraparesis/HTLV-1-associated myelopathy in about 5% of infected individuals. Expression of the virus depends on the concerted action of Tax, which drives transcription of the viral genome, and Rex, which favors expression of incompletely spliced mRNAs and determines a 2-phase temporal pattern of virus expression. The findings reported in this study revealed a novel cis-acting regulatory element and indicated that mitosis partially bypasses the requirement for Rex to export Rex-dependent HTLV-1 transcripts. Our results add a layer of complexity to the mechanisms controlling the expression of alternatively spliced HTLV-1 mRNAs and suggest a link between the cycling properties of the host cell and the temporal pattern of viral expression/latency that might influence the ability of the virus to spread and evade the immune system.
authors.affiliation: Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Cavallari
authors.affiliation: Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Rende
authors.affiliation: Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, Maryland, USA.
authors.forename: Marion K
authors.initials: MK
authors.lastname: Bona
authors.affiliation: Basic Research Laboratory, National Cancer Institute, Frederick, Maryland, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Sztuba-Solinska
authors.affiliation: Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy.
authors.forename: Micol
authors.initials: M
authors.lastname: Silic-Benussi
authors.affiliation: Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Tognon
authors.affiliation: Basic Research Laboratory, National Cancer Institute, Frederick, Maryland, USA.
authors.forename: Stuart F J
authors.identifier: http://orcid.org/0000-0001-5818-8796
authors.initials: SF
authors.lastname: LeGrice
authors.affiliation: Animal Models and Retroviral Vaccines Section, National Cancer Institute, Bethesda, Maryland, USA.
authors.forename: Genoveffa
authors.initials: G
authors.lastname: Franchini
authors.affiliation: Department of Biomedical Sciences, University of Padua, Padua, Italy.
authors.forename: Donna M
authors.initials: DM
authors.lastname: D'Agostino
authors.affiliation: Department of Surgery, Oncology and Gastroenterology, University of Padua, Padua, Italy Istituto Oncologico Veneto-IRCCS, Padua, Italy v.ciminale@unipd.it.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Ciminale
mesh_terms: D015870:Gene Expression; D020869:Gene Expression Profiling; D015967:Gene Expression Regulation, Viral; D055786:Gene Knockout Techniques; D016370:Gene Products, rex / Q000172:deficiency / Q000235:genetics; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D006801:Humans; D008938:Mitosis; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D038621:Regulatory Sequences, Ribonucleic Acid
chemical_list: D016370:Gene Products, rex; D012333:RNA, Messenger; D012367:RNA, Viral; D038621:Regulatory Sequences, Ribonucleic Acid; C514844:rex Protein, Human T-lymphotropic virus 1