Figure 2. Genomic PCR assay of MRE11 intron 4 T₁₁ tract.

(A) Diagram of the MRE11 intron 4/exon 5 junction, showing the T₁₁ tract in intron 4, flanking sequence and primers. Contraction of the T₁₁ tract impairs the lariat formation step in mRNA splicing and leads to skipping of exon 5. The resulting mutant mRNA encodes a truncated MRE11 polypeptide with potentially dominant negative effect on protein function [12]. MRE11 is essential for cell viability, and the MRE11 mutations that occur in MMR-D CRC are not null alleles but reduce expression and activity of the MRE11 protein. (B) Sequence traces of the region of MRE11 intron 4 that carries the T₁₁ tract in four tumor samples. Lengths of tracts in nt shown at left.