The budding yeast histone H3 variant, Cse4, replaces conventional histone H3 in centromeric chromatin and, together with centromere-specific DNA-binding factors, directs assembly of the kinetochore, a multiprotein complex mediating chromosome segregation. We have identified Scm3, a nonhistone protein that colocalizes with Cse4 and is required for its centromeric association. Bacterially express...

hTERT, the human telomerase reverse transcriptase, is highly expressed in stem cells and embryonic tissues but undetectable in most adult somatic cells. To understand its repression mechanisms in somatic cells, we investigated the endogenous hTERT gene regulation during differentiation of human leukemic HL60 cells. Our study revealed that silencing of the hTERT promoter was a biphasic process. ...

The nucleosome. Digital model of a nucleosome, the fundamental structural unit of chromosomes in the eukaryotic cell nucleus, derived from X-ray crystallography data. Each nucleosome consists of a core group of histone proteins (orange) wrapped in chromosomal DNA (green). The nucleosome is a structure responsible for regulating genes and condensing DNA strands to fit into the cell's nucleus. Re...

The 100 copies of tandemly arrayed Drosophila linker (H1) and core (H2A/B and H3/H4) histone gene cluster are coordinately regulated during the cell cycle. However, the molecular mechanisms that must allow differential transcription of linker versus core histones prevalent during development remain elusive. Here, we used fluorescence imaging, biochemistry, and genetics to show that TBP (TATA-bo...

Gene promoters perceive numerous signals and integrate this information into a single response, the transcriptional activity of a gene. It was speculated that covalent modification of histones on the promoters might have an important function in storage and integration of signals. Using the genes for the core proteins of C4 metabolism in maize as a model, we associated the perception of specifi...

Mutations in the l(3)mbt tumour suppressor result in overproliferation of Drosophila larval brains. Recently, the derepression of different gene classes in l(3)mbt mutants was shown to be causal for transformation. However, the molecular mechanisms of dL(3)mbt-mediated gene repression are not understood. Here, we identify LINT, the major dL(3)mbt complex of Drosophila. LINT has three core subun...

We have studied the functional properties of iodinated histones. Isolated, denatured histones were iodinated at trace levels and then renatured together with carrier histones and high molecular weight DNA to form nucleohistone. Nucleosomes were prepared from the reconstitute using micrococcal nuclease, and the relative representations of the individual iodinated tyrosines of the histones in the...

We present here a cytosolic tether-and-release system to study the import and dynamics of newly synthesised nuclear proteins. Release is gated by rapamycin-induced recruitment and activation of a viral protease, with cleavage of a peptide linker releasing the tethered cargo. We use this system to investigate nucleo-cytoplasmic divisions in the histone H3.1 & H4 deposition pathway, revealing tha...

The histone gene cluster on mouse chromosome 3 has been isolated as a series of overlapping P1 clones, covering 110-120 kb, by probing with the histone H3-614 gene that had been mapped previously to mouse chromosome 3. There are genes for 10 core histone proteins present in a 55-kb cluster within this contig. There are three histone H3 genes, two of which are identical; four histone H2a genes, ...

The mouse mammary tumor virus (MMTV) promoter is regulated by steroid hormones through a hormone-responsive region that is organized in a positioned nucleosome. Hormone induction leads to a structural change of this nucleosome which makes its DNA more sensitive to cleavage by DNase I and enables simultaneous binding of all relevant transcription factors. In cells carrying either episomal or chr...