FBL and infection: The location of EGFP-tagged B23 (a nucleo-cytoplasmic shuttling protein), upstream binding factor (UBF, a nucleolar transcription factor) or fibrillarin (found in the dense fibrillar component (DFC) of the nucleolus) remained unchanged after a 3 h EPEC infection (Figure 4A) - despite extensive nucleolin redistribution in the same cells (Figure S3A).