• 14-3-3 proteins are constituents of the insoluble glycoprotein framework of the chlamydomonas cell wall.

      Voigt, Jürgen; Frank, Ronald; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2003-06)
      The cell wall of the unicellular green alga Chlamydomonas reinhardtii consists predominantly of Hyp-rich glycoproteins, which also occur in the extracellular matrix of multicellular green algae and higher plants. In addition to the Hyp-rich polypeptides, the insoluble glycoprotein framework of the Chlamydomonas cell wall contains minor amounts of 14-3-3 proteins, as revealed by immunochemical studies and mass spectroscopic analysis of tryptic peptides. Polypeptides immunologically related to the 14-3-3 proteins also were found in the culture medium of Chlamydomonas. The levels of two of these 14-3-3-related polypeptides were decreased in the culture medium of the wall-deficient mutant cw-15. These findings indicate that 14-3-3 proteins are involved in the cross-linking of Hyp-rich glycoproteins in the Chlamydomonas cell wall.
    • Kaposi's sarcoma-associated herpesvirus viral interferon regulatory factor 4 (vIRF4/K10) is a novel interaction partner of CSL/CBF1, the major downstream effector of Notch signaling.

      Heinzelmann, Katharina; Scholz, Barbara A; Nowak, Agnes; Fossum, Even; Kremmer, Elisabeth; Haas, Juergen; Frank, Ronald; Kempkes, Bettina; Helmholtz Centre for infection research. Inhoffenstr. 7. 38124 Braunschweig, Germany. (2010-12)
      In cells infected with the Kaposi's sarcoma-associated herpesvirus (KSHV), CSL/CBF1 signaling is essential for viral replication and promotes the survival of KSHV-infected cells. CSL/CBF1 is a DNA adaptor molecule which recruits coactivator and corepressor complexes to regulate viral and cellular gene transcription and which is a major downstream effector molecule of activated Notch. The interaction of KSHV RTA and LANA with CSL/CBF1 has been shown to balance the lytic and latent viral life cycle. Here we report that a third KSHV protein, viral interferon regulatory factor 4 (vIRF4/K10), but none of the three other KSHV-encoded vIRFs, interacts with CSL/CBF1. Two regions of vIRF4 with dissimilar affinities contribute to CSL/CBF1 binding. Similar to Notch, vIRF4 targets the hydrophobic pocket in the beta trefoil domain of CSL/CBF1 through a short peptide motif which closely resembles a motif found in Notch but does not strictly follow the ΦWΦP consensus conserved in human and mouse Notch proteins. Our results suggest that vIRF4 might compete with Notch for CSL/CBF1 binding and signaling.