Detailed analysis of the nucleosomal organization of transcribed DNA in yeast chromatin.

The precise chromatin structure of actively transcribed DNA in yeast has been analyzed by electrophoretic transfer of high-resolution staphylococcal nuclease and DNase I chromatin digest DNA patterns to DBM paper and hybridization with active sequence probes. The DNA patterns of the transcribed DNA sequences resemble the DNA patterns produced by digestion of bulk yeast nucleosomes. Hence, these active sequences must be arranged in "typical" nucleosome structures. Furthermore, in details of the structure, the active sequence nucleosomes look almost exactly like the average yeast nucleosome in repeat length, in the length of DNA associated with the core particle, in the amount and type of heterogeneity found within and between the oligomeric and monomeric repeat lengths of DNA, in the occurrence of discrete spacer lengths including the characteristic five nucleotide increments (i.e., 5, 15, 25, ... base pairs), and in the length of DNA between yeast nucleosomes. Early in digestion, there are some differences: increases in peak breadths (i.e., in the distribution of spacer lengths) and some preferential release of monomer DNA. These results suggest that transcribed DNA can exist in the typical (yeast) type of nucleosome organization and thus that active chromatin regions do not necessarily require profound structural rearrangements. The slight differences noted are consistent with some slight, mainly spacer, modification in the vicinity of the transcription event itself.