title: Inner nuclear membrane proteins Asi1, Asi2, and Asi3 function in concert to maintain the latent properties of transcription factors Stp1 and Stp2.
abstract: In yeast the homologous transcription factors Stp1 and Stp2 are synthesized as latent cytoplasmic precursors with N-terminal regulatory domains. In response to extracellular amino acids the regulatory domains are endoproteolytically excised by the plasma membrane-localized SPS sensor. The processed forms of Stp1 and Stp2 efficiently enter the nucleus and induce expression of amino acid permease genes. We recently reported that the inner nuclear membrane protein Asi1 is required to prevent unprocessed forms of Stp1 and Stp2, which ectopically enter the nucleus, from binding SPS sensor-regulated promoters. Here we show that Asi3, an Asi1 homolog, and Asi2 are integral proteins of the inner nuclear membrane that function in concert with Asi1. In cells lacking any of the three Asi proteins, unprocessed full-length forms of Stp1 and Stp2 constitutively induce SPS sensor-regulated genes. Our results demonstrate that the Asi proteins ensure the fidelity of SPS sensor signaling by maintaining the dormant, or repressed state, of gene expression in the absence of inducing signals. This study documents additional components of a novel mechanism controlling transcription in eukaryotic cells.
authors.affiliation: Ludwig Institute for Cancer Research, Karolinska Institute, Stockholm, Sweden.
authors.forename: Arezou
authors.initials: A
authors.lastname: Zargari
authors.forename: Mirta
authors.initials: M
authors.lastname: Boban
authors.forename: Stijn
authors.initials: S
authors.lastname: Heessen
authors.forename: Claes
authors.initials: C
authors.lastname: Andréasson
authors.forename: Johan
authors.initials: J
authors.lastname: Thyberg
authors.forename: Per O
authors.initials: PO
authors.lastname: Ljungdahl
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006031:Glycosylation; D008565:Membrane Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C438144:ASI1 protein, S cerevisiae; C438145:ASI3 protein, S cerevisiae; C516922:Asi2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; C074632:STP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C421606:Stp2 protein, S cerevisiae; D014157:Transcription Factors