title: Nuclear and nucleolar targeting sequences of c-erb-A, c-myb, N-myc, p53, HSP70, and HIV tat proteins.
abstract: Protein import into the cell nucleus requires specific binding of nuclear proteins to the nuclear pore complex. Based on amino acid sequence "motifs" of known nuclear targeting signals, we identified peptides within a number of nuclear proteins with likely nuclear targeting potential and tested their function by transfecting into cells fusion genes that produce the cytoplasmic "reporter" protein, pyruvate kinase (PK), joined to the test sequence. Sequences within c-myb (PLLKKIKQ), N-myc (PPQKKIKS), p53 (PQPKKKP), and c-erb-A (SKRVAKRKL) oncoproteins that direct PK hybrids into the nucleus were identified. A peptide (GRKKRRQRRRAP) of the human immunodeficiency virus (HIV) tat protein (Tat), which contains two short basic regions, targets fusion proteins to the nucleolus. The COOH-terminal basic Tat region (QRRRAP) does not target PK hybrid proteins into the nucleus, but mutation of two basic amino acids in this region decreases but does not abolish nucleolar accumulation mediated by the entire Tat nucleolar targeting sequence. Moreover, the c-Myc nuclear targeting sequence fused to the COOH-terminal basic Tat region (PAAKRVKLDQRRRAP) effectively localizes PK hybrids to the nucleus and nucleolus. A similar sequence (FKRKHKKDISQNKRAVRR) in the human heat-shock protein HSP70 also localizes PK to the nucleus and nucleolus.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: C V
authors.initials: CV
authors.lastname: Dang
authors.forename: W M
authors.initials: WM
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D015696:Gene Products, tat / Q000235:genetics*; D006678:HIV / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics*; D010750:Phosphoproteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020598:Proto-Oncogene Proteins c-myb; D016271:Proto-Oncogene Proteins c-myc; D011519:Proto-Oncogenes; D011770:Pyruvate Kinase / Q000235:genetics; D011988:Receptors, Thyroid Hormone; D015534:Trans-Activators / Q000235:genetics*; D016159:Tumor Suppressor Protein p53; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D006360:Heat-Shock Proteins; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D016271:Proto-Oncogene Proteins c-myc; D011988:Receptors, Thyroid Hormone; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D054322:tat Gene Products, Human Immunodeficiency Virus; D011770:Pyruvate Kinase