Interaction of SET domains with histones and nucleic acid structures in active chromatin

Changes in the normal program of gene expression are the basis for a number of human diseases. Epigenetic control of gene expression is programmed by chromatin modifications—the inheritable “histone code”—the major component of which is histone methylation. This chromatin methylation code of gene activity is created upon cell differentiation and is further controlled by the “SET” (methyltransferase) domain proteins which maintain this histone methylation pattern and preserve it through rounds of cell division. The molecular principles of epigenetic gene maintenance are essential for proper treatment and prevention of disorders and their complications. However, the principles of epigenetic gene programming are not resolved. Here we discuss some evidence of how the SET proteins determine the required states of target genes and maintain the required levels of their activity. We suggest that, along with other recognition pathways, SET domains can directly recognize the nucleosome and nucleic acids intermediates that are specific for active chromatin regions

Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals

Author Posting. © Springer, 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ecotoxicology 16 (2007): 205-219, doi:10.1007/s10646-006-0122-0.Investigative efforts into the potential endocrine-disrupting effects of chemicals have mainly concentrated on vertebrates, with significantly less attention paid to understanding potential endocrine disruption in the invertebrates. Given that invertebrates account for at least 95% of all known animal species and are critical to ecosystem structure and function, it remains essential to close this gap in knowledge and research. The lack of progress regarding endocrine disruption in invertebrates is still largely due to: (1) our ignorance of mode-of-action, physiological control, and hormone structure and function in invertebrates; (2) lack of a standardized invertebrate assay; (3) the irrelevance to most invertebrates of the proposed activity-based biological indicators for endocrine disruptor exposure (androgen, estrogen and thyroid); (4) limited field studies. Past and ongoing research efforts using the standard invertebrate toxicity test model, the mysid shrimp, have aimed at addressing some of these issues. The present review serves as an update to a previous publication on the use of mysid shrimp for the evaluation of endocrine disruptors (Verslycke et al., 2004a). It summarizes recent investigative efforts that have significantly advanced our understanding of invertebrate-specific endocrine toxicity, population modeling, field studies, and transgeneration standard test development using the mysid model.Supported by a Fellowship of the Belgian American Educational Foundation

Bladder and Bowel Dysfunction Is Common in Both Men and Women with Mutation of the ABCD1 Gene for X-Linked Adrenoleukodystrophy

Background: X-linked adrenoleukodystrophy (X-ALD) is a disorder caused by mutations in the ABCD1 gene. The commonest phenotype of X-ALD is adrenomyeloneuropathy (AMN), which is characterised by involvement of the spinal cord and peripheral nerves. The aim of this study was to evaluate bladder and bowel symptoms in men with AMN and female X-ALD carriers. Methods: In this cross-sectional study, patients with confirmed mutation of the ABCD1 gene attending a tertiary care service were approached about bladder and bowel complaints and completed the Urinary Symptom Profile (USP), Qualiveen Short Form (SF-Qualiveen), International Prostate Symptom Score (IPSS) and Neurogenic Bowel Dysfunction (NBD) questionnaires. Neurological disability was assessed using the Expanded Disability Status Scale (EDSS). Results: Forty-eight patients participated, 19 males (mean EDSS score (n = 16) 5.0 (95% CI ± 1.03)) and 29 females (mean EDSS score (n = 25) 3.2 (95% CI ± 0.98)). Overactive bladder (OAB) symptoms were reported in both males (100%, n = 19) and females (86.2%, n = 25). There was no significant gender difference in severity of OAB symptoms (P = 0.35) and impact on quality of life (P = 0.13). Furthermore, there was no significant difference in OAB severity when symptoms were compared between female carriers and a cohort of women (n = 17) with spinal cord damage due to multiple sclerosis (P = 0.27). Twenty-one percent (n = 4) of males and 10% (n = 3) of females had moderate to severe bowel dysfunction. Conclusions: Bladder and bowel complaints are common in both men with AMN and female carriers. They have a significant impact on the quality of life yet are under-reported and under-treated. Though having an X-linked pattern of inheritance, female carriers may experience overactive bladder symptoms which are as severe as in male patients and are likely to be neurological in origin

Autoregulatory control of the p53 response by caspase-mediated processing of HIPK2

The serine/threonine kinase HIPK2 phosphorylates the p53 protein at Ser 46, thus promoting p53-dependent gene expression and subsequent apoptosis. Here, we show that DNA damaging chemotherapeutic drugs cause degradation of endogenous HIPK2 dependent on the presence of a functional p53 protein. Early induced p53 allows caspase-mediated cleavage of HIPK2 following aspartic acids 916 and 977. The resulting C-terminally truncated HIPK2 forms show an enhanced induction of the p53 response and cell death, thus allowing the rapid amplification of the p53-dependent apoptotic program during the initiation phase of apoptosis by a regulatory feed-forward loop. The active HIPK2 fragments are further degraded during the execution and termination phase of apoptosis, thus ensuring the occurrence of HIPK2 signaling only during the early phases of apoptosis induction

NAD(+)-SIRT1 control of H3K4 trimethylation through circadian deacetylation of MLL1.

The circadian clock controls the transcription of hundreds of genes through specific chromatin-remodeling events. The histone methyltransferase mixed-lineage leukemia 1 (MLL1) coordinates recruitment of CLOCK-BMAL1 activator complexes to chromatin, an event associated with cyclic trimethylation of histone H3 Lys4 (H3K4) at circadian promoters. Remarkably, in mouse liver circadian H3K4 trimethylation is modulated by SIRT1, an NAD(+)-dependent deacetylase involved in clock control. We show that mammalian MLL1 is acetylated at two conserved residues, K1130 and K1133. Notably, MLL1 acetylation is cyclic, controlled by the clock and by SIRT1, and it affects the methyltransferase activity of MLL1. Moreover, H3K4 methylation at clock-controlled-gene promoters is influenced by pharmacological or genetic inactivation of SIRT1. Finally, levels of MLL1 acetylation and H3K4 trimethylation at circadian gene promoters depend on NAD(+) circadian levels. These findings reveal a previously unappreciated regulatory pathway between energy metabolism and histone methylation