Global Transcription Regulators of Eukaryotes

et al., 1975). The nucleosome core is composed of an octamer of four highly folded proteins, H2A, H2B, H3, and H4 (two of each protein), and of 147 base pairs of independent of the DNA sequence. Networks of ordered 69126 Heidelberg water molecules are found at the histone–subunit inter-Germany faces and at histone–DNA contact sites. They might thus Institute for Molecular Biology and Biophysics modulate the dissociation of the octamer into dimers ETH-Hö nggerberg HPM and tetramers, depending on salt concentration and en-8093 Zü rich tropic effects, and possibly permit the DNA to detach Switzerland over as much as one half of the superhelix to allow transcription of nucleosomal DNA without being completely dissociated from the octamer. The fields of transcriptional regulation and chromatin Formation of higher order chromatin is dependent on structure and function have for a long time been sepa-divalent ions, and interestingly, the 2.0 A ˚ structure lo-rate with too little interdisciplinary communication. The cates a manganese ion bound in perfect octahedral co-two fields have now merged with advances in the com-ordination between two core particles. Only about one plete description of all factors that are required for basal, third of the flexible N-terminal histone tails is visible in nonregulated transcription, the availability of highly puri-the structure and reaches out between and around the fied in vitro transcription systems, and the purification gyres of the DNA superhelix. The disordered structure of several large complexes with chromatin remodeling of the tails suggests that they are primarily involved in activities. Thus, it is now possible to start studying the higher order interactions. biologically important question: How is transcription The location of linker histone binding relative to the regulated in a chromatin context? To discuss this issue, core particle DNA has been the subject of several stud-scientists from the two fields met in Strasbourg, France ies yielding conflicting results. Andrew Travers reported (December 3–5, 1998) at a workshop titled " Global Tran-results on the binding site of linker histone H5 on mixed scription Regulators of Eukaryotes, " arranged by the sequence chicken DNA chromatosomes, structural units International Human Frontier Science Program. We have of chromatin in chicken erythrocytes comprised of a chosen to focus this report on the most recent results nucleosome core, its DNA extension, and one linker presented at the workshop and would like to refer the histone molecule. The globular domain of the linker his-reader to the …