title: Expression-site-associated gene 8 (ESAG8) of Trypanosoma brucei is apparently essential and accumulates in the nucleolus.
abstract: Trypanosoma brucei variant surface glycoprotein expression sites are interesting examples of genomic loci under complex epigenetic control. In the infectious bloodstream stage, only one of about 20 expression sites is actively transcribed. In the Tsetse midgut (procyclic) stage, chromatin remodeling silences all expression sites. We have begun to explore the function of one of the expression-site-associated genes, ESAG8. Gene knockout experiments implied that ESAG8 is essential. ESAG8 is present at a very low level and apparently accumulates in the nucleolus. A 32-amino-acid domain, which contains a putative bipartite nuclear localization signal (NLS), is both necessary and sufficient to target fusions of ESAG8, with Aequorea victoria green fluorescent protein, to the trypanosome nucleolus. This same sequence functioned only as an NLS in mammalian cells, supporting the idea that nucleolar accumulation requires specific interactions. These results have implications for models of ESAG8 function.
authors.affiliation: Laboratory of Molecular Parasitology, The Rockefeller University, New York, NY 10021, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hoek
authors.forename: M
authors.initials: M
authors.lastname: Engstler
authors.forename: G A
authors.initials: GA
authors.lastname: Cross
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002466:Cell Nucleolus / Q000235:genetics* / Q000648:ultrastructure; D003001:Cloning, Molecular; D017353:Gene Deletion; D005786:Gene Expression Regulation; D020043:Genes, Essential; D017125:Genes, Protozoan / Q000235:genetics; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D011994:Recombinant Proteins / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014162:Transfection; D014346:Trypanosoma brucei brucei / Q000235:genetics*
chemical_list: D008164:Luminescent Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C066671:ESAG 8 protein, Trypanosoma brucei; D049452:Green Fluorescent Proteins