Figure 8. .

Residual FANCD2 protein. A, Exon 23 sequence following that of exon 21 (exon 22 exclusion, aberrant splicing), which prevails in cDNA from homozygotes for the splice-acceptor mutation in intron 21, c.1948-16T→G, but, at low level, underlying sequence is readable as exon 22 (exon inclusion). Depicted are results from patient 5. B, Blood-derived cells from nonmosaic FA-D2 patients (exemplified 13, 5, 1, 21, 2, 6, 11, and 28) show faint but conspicuous FANCD2 bands of both species in response to MMC exposure exclusively on overexposed immunoblots, as indicated by the very intense FANCD2 signals of the normal controls (CON) (patient 13, stimulated PBL; patients 5, 1, 21, 2, 6, 11, and 28, LCLs; loading control RAD50). The individual abundance of residual protein varies considerably at low levels. C, LCLs were subjected to the indicated concentrations of hydroxyurea (HU) for 16 h. On an overexposed blot, the FANCD2-L band of the residual protein in the LCL from patient 21 increases with the HU concentration in a dose-dependent response. Normal control LCLs are distinctive by their prominent FANCD2 signals.