Figure 6.

Demonstration that the Tec element chromatin structure is uniform across the element and that the chromatin is organized in nucleosomes. Four sets of three MNase samples from total nuclei at 43 h of development (corresponding to 0.25 U/ml MNase at 30 and 45 min and 1.25 U/ml MNase at 10 min, as in Figure 3) were electrophoresed in 1.5% agarose, Southern blotted, and hybridized consecutively with 11 different Tec1 probes ranging in size from 80 to 250 bp. The two types of hybridization patterns obtained are shown for one blot probed with two different probes. (B) The Tec1 element is shown, with the black boxes indicating the positions of the restriction fragments used as small probes. The four fragments with stars above them gave the hybridization pattern seen with probe 1, in which little detection of submonomer fragment sizes is seen. The rest of the fragments gave a pattern identical to that seen with probe 2, in which both the ∼300-bp unusual “dimer” size and smaller fragments are observed. (C) Anlagen purified from cells at 45 h of development were treated with varying amounts (10-fold differences) of trypsin before digestion with MNase (see MATERIALS AND METHODS). All five samples designated +MNase were digested identically with MNase. The −MNase lane contains DNA isolated from untreated nuclei. Samples were electrophoresed on 1.5% agarose gels, Southern blotted, and hybridized with a Tec element probe. The marker lane is a 100-bp ladder with sizes indicated in base pairs.