西亚试剂：A Packing Mechanism for Nucleosome Organization Reconstitut

A Packing Mechanism for Nucleosome Organization Reconstituted Across a Eukaryotic Genome

Zhang, Zhenhai; Wippo, Christian J.; Wal, Megha; Ward, Elissa; Korber, Philipp; Pugh, B. Franklin

Near the 5′ end of most eukaryotic genes, nucleosomes form highly regular arrays that begin at canonical distances from thetranscriptional start site. Determinants of this and other aspects of genomic nucleosome organization have been ascribed tostatistical positioning, intrinsically DNA-encoded positioning, or some aspect of transcription initiation. Here, we provideevidence for a different explanation. Biochemical reconstitution of proper nucleosome positioning, spacing, and occupancylevels was achieved across the 5′ ends of most yeast genes by adenosine triphosphate–dependent trans-acting factors. Thesetranscription-independent activities override DNA-intrinsic positioning and maintain uniform spacing at the 5′ ends of geneseven at low nucleosome densities. Thus, an active, nonstatistical nucleosome packing mechanism creates chromatin organizingcenters at the 5′ ends of genes where important regulatory elements reside.