The FUBP1 and FIR enrichment normally detected on FUSE are no longer observed at the MYC TSS in cell lines derived from XP patients with C-terminally truncated XPB, suggesting a failure to form the FUBP1-FIR-XPB/TFIIH bridge as a consequence of the defective interaction between XPB and FIR. Here, ERCC3 is linked to xeroderma pigmentosum.