Fig. 4.

Matrix attachment properties of DNA in the neighborhood of the chicken HS4 insulator. (A) An in vivo MAR assay of the endogenous HS4 insulator. Matrices from pre-erythroid 6C2 cells or primary 10-d RBCs were prepared by using the lithium salt extraction procedure to preserve native attachment sites. After extensive DNase I digestion, residual DNA fragments were precipitated and analyzed by quantitative PCR by using primers across the chicken β-globin locus. Only DNA fragments of the HS4 insulator remained. (B) Representation of PCR analyses of matrices from 6C2 cells centered on the HS4 core and surrounding sequences. All primer sets were tested with genomic DNA. Open bars represent amplified regions for the genomic DNA but were absent from the matrix preparation. Filled bars represent amplified products for both genomic and matrix DNA samples.