title: Biochemical and NMR study on the competition between proteins SC35, SRp40, and heterogeneous nuclear ribonucleoprotein A1 at the HIV-1 Tat exon 2 splicing site.
abstract: The human immunodeficiency virus, type 1, Tat protein plays a key role in virus multiplication. Because of its apoptotic property, its production is highly controlled. It depends upon the A3 splicing site utilization. A key control of site A3 activity is the ESS2 splicing silencer, which is located within the long stem-loop structure 3 (SLS3), far downstream from site A3. Here, by enzymatic footprints, we demonstrate the presence of several heterogeneous nuclear ribonucleoprotein (hnRNP) A1-binding sites on SLS3 and show the importance of the C-terminal Gly domain of hnRNP A1 in the formation of stable complexes containing several hnRNP A1 molecules bound on SLS3. Mutations in each of the UAG triplets in ESS2 strongly reduce the overall hnRNP A1 binding, showing the central role of ESS2 in hnRNP A1 assembly on SLS2-SLS3. Using NMR spectroscopy, we demonstrate the direct interaction of ESS2 with the RNA recognition motifs domains of hnRNP A1. This interaction has limited effect on the RNA two-dimensional structure. The SR proteins SC35 and SRp40 were found previously to be strong activators of site A3 utilization. By enzymatic and chemical footprints, we delineate their respective binding sites on SLS2 and SLS3 and find a strong similarity between the hnRNP A1-, SC35-, and SRp40-binding sites. The strongest SC35-binding site only has a modest contribution to site A3 activation. Hence, the main role of SR proteins at site A3 is to counteract hnRNP A1 binding on ESS2 and ESE2. Indeed, we found that ESE2 has inhibitory properties because of its ability to bind hnRNP A1.
authors.affiliation: UMR 7567 CNRS-Université Henri Poincaré-Nancy I, Boulevard des Aiguillettes, BP239, 54506 Vandoeuvre-lès-Nancy Cedex and Laboratoire de Chimie et Biologie Structurales, ICSN-CNRS, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette, France.
authors.forename: Houda
authors.initials: H
authors.lastname: Hallay
authors.forename: Nicolas
authors.initials: N
authors.lastname: Locker
authors.forename: Lilia
authors.initials: L
authors.lastname: Ayadi
authors.forename: Delphine
authors.initials: D
authors.lastname: Ropers
authors.forename: Eric
authors.initials: E
authors.lastname: Guittet
authors.forename: Christiane
authors.initials: C
authors.lastname: Branlant
mesh_terms: D020816:Amino Acid Motifs; D001483:Base Sequence; D001665:Binding Sites; D005091:Exons; D015696:Gene Products, tat / Q000235:genetics*; D016679:Genome, Viral; D015497:HIV-1 / Q000235:genetics*; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000502:physiology*; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000502:physiology*; D000068103:Serine-Arginine Splicing Factors; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; C000619656:hnRNPA1 protein, human; D054322:tat Gene Products, Human Immunodeficiency Virus; C073288:SRSF2 protein, human; D000068103:Serine-Arginine Splicing Factors