Increasing the rate of chromatin remodeling and gene activation—a novel role for the histone acetyltransferase Gcn5

Histone acetyltransferases (HATs) such as Gcn5 play a role in transcriptional activation. However, the majority of constitutive genes show no requirement for GCN5, and even regulated genes, such as the yeast PHO5 gene, do not seem to be affected significantly by its absence under normal activation conditions. Here we show that even though the steady-state level of activated PHO5 transcription is not affected by deletion of GCN5, the rate of activation following phosphate starvation is significantly decreased. This delay in transcriptional activation is specifically due to slow chromatin remodeling of the PHO5 promoter, whereas the transmission of the phosphate starvation signal to the PHO5 promoter progresses at a normal rate. Chromatin remodeling is equally delayed in a galactose-inducible PHO5 promoter variant in which the Pho4 binding sites have been replaced by Gal4 binding sites. By contrast, activation of the GAL1 gene by galactose addition occurs with normal kinetics. Lack of the histone H4 N-termini leads to a similar delay in activation of the PHO5 promoter. These results indicate that one important contribution of HATs is to increase the rate of gene induction by accelerating chromatin remodeling, rather than to affect the final steady-state expression levels

Purification and characterization of the human Elongator complex

Human Elongator complex was purified to virtual homogeneity from HeLa cell extracts. The purified factor can exist in two forms: a six-subunit complex, holo-Elongator, which has histone acetyltransferase activity directed against histone H3 and H4, and a three-subunit core form, which does not have histone acetyltransferase activity despite containing the catalytic Elp3 subunit. Elongator is a component of early elongation complexes formed in HeLa nuclear extracts and can interact directly with RNA polymerase II in solution. Several human homologues of the yeast Elongator subunits were identified as subunits of the human Elongator complex, including StIP1 (STAT-interacting protein 1) and IKAP (IKK complex-associated protein). Mutations in IKAP can result in the severe human disorder familial dysautonomia, raising the possibility that this disease might be due to compromised Elongator function and therefore could be a transcription disorder

Hereditary dysautonomias: current knowledge and collaborations for the future

The hereditary dysautonomias (H-Dys) are a large group of disorders that affect the autonomic nervous system. Research in the field of H-Dys is very challenging, because the disorders involve interdisciplinary, integrative, and "mind-body" connections. Recently, medical scientists, NIH/NINDS representatives, and several patient support groups gathered for the first time in order to discuss recent findings and future directions in the H-Dys field. The H-Dys workshop was instrumental in promoting interactions between basic science and clinical investigators. It also allowed attendees to have an opportunity to meet each other, understand the similarities between the various forms of dysautonomia, and experience the unique perspective offered by patients and their families. Future advances in H-Dys research will depend on a novel multi-system approach by investigators from different medical disciplines, and it is hoped that towards a common goal, novel "bench-to-bedside" therapeutics will be developed to improve the lives of, or even cure, patients suffering from dysautonomic syndromes