The DNA-binding domain of two bZIP transcription factors, the Epstein-Barr virus switch gene product EB1 and Jun, is a bipartite nuclear targeting sequence.
The Epstein-Barr virus BZLF1 gene product EB1 (also called ZEBRA and Zta), is a transcription factor belonging to the bZIP (basic domain leucine zipper) family of nuclear proteins. Translocation to the nucleus of EB1 (J. Becker, U. Leser, M. Marschall, A. Langford, W. Jilg, H. Gelderblom, P. Reichart, and H. Wolf, Proc. Natl. Acad. Sci. USA 88:8332-8336, 1991) and of two other bZIP proteins, c-Jun and c-Fos (P. Roux, J.-M. Blanchard, A. Fernandez, N. Lamb, P. Jeanteur, and M. Piechaczyk, Cell 63:341-351, 1990), has been shown to be subject to regulation. We show here that for both EB1 and Jun the nuclear targeting signals (NTS) in the proteins' primary sequences are two clusters of positively charged amino acids. These clusters, called BRA and BRB, are necessary and sufficient to direct beta-galactosidase to the nuclear compartment and act as a bipartite NTS. They are conserved among all the bZIP proteins, and although they are not identical, they probably share the same function. Site-directed mutagenesis studies made on these basic clusters suggest that they also act as a bipartite NTS in the EB1 protein. Our results also demonstrate that in EB1 and Jun, these bipartite NTS are superimposed with bipartite DNA-binding domains, since BRA and BRB are required in vitro for direct and specific contact between these proteins and their DNA-binding sites.
ENS-CNRS UMR49, Ecole Normale Supérieure de Lyon, France.
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I
Mikaélian
E
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Drouet
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Marechal
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Denoyel
J C
JC
Nicolas
A
A
Sergeant
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005812:Genes, Switch; D004854:Herpesvirus 4, Human / Q000235:genetics*; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D014764:Viral Proteins
C063676:BZLF1 protein, Herpesvirus 4, Human; D004268:DNA-Binding Proteins; D021382:Protein Sorting Signals; D016755:Proto-Oncogene Proteins c-jun; D015534:Trans-Activators; D014157:Transcription Factors; D014764:Viral Proteins