title: NOA36 protein contains a highly conserved nucleolar localization signal capable of directing functional proteins to the nucleolus, in mammalian cells.
abstract: NOA36/ZNF330 is an evolutionarily well-preserved protein present in the nucleolus and mitochondria of mammalian cells. We have previously reported that the pro-apoptotic activity of this protein is mediated by a characteristic cysteine-rich domain. We now demonstrate that the nucleolar localization of NOA36 is due to a highly-conserved nucleolar localization signal (NoLS) present in residues 1-33. This NoLS is a sequence containing three clusters of two or three basic amino acids. We fused the amino terminal of NOA36 to eGFP in order to characterize this putative NoLS. We show that a cluster of three lysine residues at positions 3 to 5 within this sequence is critical for the nucleolar localization. We also demonstrate that the sequence as found in human is capable of directing eGFP to the nucleolus in several mammal, fish and insect cells. Moreover, this NoLS is capable of specifically directing the cytosolic yeast enzyme polyphosphatase to the target of the nucleolus of HeLa cells, wherein its enzymatic activity was detected. This NoLS could therefore serve as a very useful tool as a nucleolar marker and for directing particular proteins to the nucleolus in distant animal species.
authors.affiliation: Departamento de Biomedicina, Biotecnología y Salud Pública-Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain.
authors.forename: Ivan S
authors.initials: IS
authors.lastname: de Melo
authors.forename: Maria D
authors.initials: MD
authors.lastname: Jimenez-Nuñez
authors.forename: Concepción
authors.initials: C
authors.lastname: Iglesias
authors.forename: Antonio
authors.initials: A
authors.lastname: Campos-Caro
authors.forename: David
authors.initials: D
authors.lastname: Moreno-Sanchez
authors.forename: Felix A
authors.initials: FA
authors.lastname: Ruiz
authors.forename: Jorge
authors.initials: J
authors.lastname: Bolívar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D019913:Nuclear Localization Signals; C435644:ZNF330 protein, human; D049452:Green Fluorescent Proteins