Figure 2.

BLM mutation map and telomere association domains. A. Map of BLM mutations [19] and domains with assigned sequence identities. NLS indicates the basic nuclear localization signal [60]. The HRD (Helicase and RNAseD) region is common to several members of the RecQ DNA helicase family and structural modeling suggests it is a single-strand nucleic acid binding domain [31]. The red bars indicate regions with a high density of negatively charged amino acids [3]. B. ChIP mapping of the telomere association domains of BLM. Equivalent amounts of DNA recovered from the induced cell lines were denatured and transferred to a nylon membrane. Telomere repeats sequences were quantitated by hybridization with a radiolabeled complementary oligonucleotide [10] and exposure to a phosphorimager screen. Hybridization units were calculated relative to the cell line expressing EGFP alone. Values are the average of two experiments: BLM 8+/-1.4, ΔN1 7+/-0.1, ΔN2 4+/-2.8, ΔN3 1+/-0.1, ΔN4 2+/-1.4, K695T 5+/-2.8, ΔH1 5+/-0.1, ΔC1 6+/-1.4, ΔC2 7+/-1.4.