Correction

CELL BIOLOGY. For the article “Nrdp1/FLRF is a ubiquitin ligase promoting ubiquitination and degradation of the epidermal growth factor receptor family member, ErbB3,” by Xiao-Bo Qiu and Alfred L. Goldberg, which appeared in number 23, November 12, 2002, of Proc. Natl. Acad. Sci. USA (99, 14843–14848; First Published October 31, 2002; 10.1073/pnas.232580999), Fig. 4 should have appeared in color. In addition, the marker for the Ub band of Fig. 6A should be 14. The corrected figures and their legends appear below.

Fig 4.

Nrdp1 reduces levels of endogenous ErbB3. MDA-MB-468 cells were transfected with FLAG-tagged Nrdp1 or Nrdp1C. Localization of Nrdp1, Nrdp1C, ErbB3, or EGFR was visualized by confocal fluorescence microscopy after incubation with appropriate primary antibodies and FITC or Cy3 conjugates of secondary antibodies. Different images on each row, which are representative of many (>30) microscopic fields, are the same cells with different kinds of staining. The cells transfected with Nrdp1 or Nrdp1C are indicated by arrowheads. The nuclei of cells were visualized under UV light after staining with 4′,6-diamidino-2-phenylindole.

Fig 6.

Nrdp1 is a ubiquitin ligase promoting ubiquitination of itself and ErbB3. (A) Nrdp1-catalyzed formation of [¹²⁵I]ubiquitin conjugates was assayed in vitro. All of the components were expressed and purified from bacteria. (B) Autoubiquitination of Nrdp1 requires its RING finger domain. Wild-type, mutant (C34S/H36Q), and truncated Nrdp1 were immunopurified from the 293T cells transfected with their FLAG-tagged form and were used for in vitro ubiquitination assay. (Left) Nrdp1 was labeled in vivo with ³⁵S. (Right) Ubiquitin was labeled with ¹²⁵I. (C) Nrdp1 stimulates ErbB3 ubiquitination in vivo. The 293T cells were transfected with ErbB3, or cotransfected with ErbB3 and the wild-type or mutant (C34S/H36Q) Nrdp1-FLAG in the presence (Left) or the absence (Right) of pCMV-myc-Ub (kindly provided by Ron Kopito, Stanford University, Stanford, CA). ErbB3 ubiquitination was detected by Western blotting by using either anti-myc antibodies (Oncogene Research Products) or anti-Ub antibodies (Zymed) after immunoprecipitation by anti-ErbB3 antibodies. Arrows indicate 191-kDa markers. (D) Nrdp1 ubiquitinates endogenous ErbB3 in vitro. ErbB3 immunoprecipitated from the MDA-MB-453 cells was incubated with the lysates of 293T cells untransfected or transfected with wild-type, mutant (C34S/H36Q), or truncated Nrdp1-FLAG in the presence of [¹²⁵I]ubiquitin (K48R mutant). The ¹²⁵I-labeled ErbB3-ubiquitin conjugates on beads were separated on SDS/PAGE and analyzed by PhosphorImager after ubiquitination assays and precipitation from the reaction mix. Arrow indicates the 191-kDa marker.