Exon 5 was replaced with one in which nucleotide substitutions result in the amino acid substitution of glutamic acid for aspartic acid at position 553 (D553E). This allele is expected to produce a SUMOylation-deficient protein. A floxed lacZ-neo cassette inserted downstream of the modified exon 5 was removed by cre-mediated recombination. (J:167521)