The Y‐box proteins are the most evolutionarily conserved nucleic acid binding proteins yet defined in bacteria, plants and animals. The central nucleic acid binding domain of the vertebrate proteins is 43% identical to a 70‐amino‐acid‐long protein (CS7.4) from E. coli. The structure of this domain consists of an antiparallel fivestranded β‐barrel that recognizes both DNA and RNA. The diverse biological roles of these Y‐box proteins range from the control of the E. coli cold‐shock stress response to the translational masking of (...) messenger RNA in vertebrate gametes. This review discusses the organization of the prokaryotic and eukaryotic Y‐box proteins, how they interact with nucleic acids, and their biological roles, both proven and potential. (shrink)

Knockout experiments in Tetrahymena show that linker histone H1 is not essential for nuclear assembly or cell viability. These results, together with a series of biochemical and cell biological observations, challenge the existing paradigm that requires linker histones to be a key organizing component of higher‐order chromatin structure. The H1 Knockouts also reveal a much more subtle role for H1. Instead of acting as a general transcriptional repressor, H1 is found to regulate a limited number of specific genes. Surprisingly, H1 (...) can both activate and repress transcription. We discuss how this architectural protein might accomplish this important regulatory role. (shrink)

Nucleosome positioning is proposed to have an essential role in facilitating the regulated transcription of eukaryotic genes. Some transcription factors can bind to DNA when it is appropriately wrapped around the histone core, others cannot bind due to the severe deformation of DNA structure. The staged assembly of nucleosomes and positioning of histone‐DNA contacts away from promoter elements can facilitate the access of transcription factors to DNA. Positioned nucleosomes can also facilitate transcription through providing the appropriate scaffolding to bring regulatory (...) factors bound at dispersed sites into juxtaposition. (shrink)

Nucleosome positioning is proposed to have an essential role in facilitating the regulated transcription of eukaryotic genes. Some transcription factors can bind to DNA when it is appropriately wrapped around the histone core, others cannot bind due to the severe deformation of DNA structure. The staged assembly of nucleosomes and positioning of histone‐DNA contacts away from promoter elements can facilitate the access of transcription factors to DNA. Positioned nucleosomes can also facilitate transcription through providing the appropriate scaffolding to bring regulatory (...) factors bound at dispersed sites into juxtaposition. (shrink)

The recent surge of discoveries concerning the structural organization of nucleosomes, together with genetic evidence of highly specialized roles for the histones in gene regulation, have brought a renewed need for a detailed understanding of nucleosomal anatomy. Here we review recent structural advances leading to a new level of understanding of the nucleosome and chromatin fibre structure. We discuss the problems and challenges for existing models of chromatin structure and, in particular, consider how linker histones may bind within the nucleosome, (...) together with the implications of their association for the structure of the chromatin fibre. (shrink)