Biomedical subjects

Sung-Hee Ahn

Publications and source records attributed to Sung-Hee Ahn.

7 recordsLinked to original sources

PubMed2006

Histone H2B deacetylation at lysine 11 is required for yeast apoptosis induced by phosphorylation of H2B at serine 10.

Chromatin alterations, induced by covalent histone modifications, mediate a wide range of DNA-templated processes, including apoptosis. Apoptotic chromatin condensation has been causally linked to the phosphorylation of histone H2B (serine 14 in human; serine 10 in yeast, H2BS10ph) in human and yeast cells. Here, we extend these studies by demonstrating a unidirectional, crosstalk pathway between H2BS10 phosphorylation and lysine 11 acetylation (H2BK11ac) in yeast. We demonstrate that the H2BK11 acetyl mark, which exists in growing yeast, is removed upon H(2)O(2) treatment but before H2BS10ph occurs, in a unidirectional fashion. H2B K11Q mutants are resistant to cell death elicited by H(2)O(2), while H2B K11R mutants that mimic deacetylation promote cell death. Our results suggest that Hos3 HDAC deacetylates H2BK11ac, which in turn mediates H2BS10ph by Ste20 kinase. Together, these studies underscore a concerted series of enzyme reactions governing histone modifications that promote a switch from cell proliferation to cell death.

Acetylation↗

PubMed2005

A study of lower urinary tract symptoms for the Korean women aged 30 and over.

The purposes of this study were (1) to identify the prevalence of urinary incontinence (UI) and lower urinary tract symptoms (LUTS) for Korean women, (2) to evaluate the LUTS scores of the subjects in relation with each UI patterns and general characteristics, and (3) to identify affecting factors developing LUTS by using self-administered questionnaire. Community-based cross-sectional study was conducted for 3,371 women aged 30 to 89 years old who were allocated at six provinces in South Korea. UI and LUTS were assessed by validated symptom scales including the International Prostate Symptom Score. Of all the respondents, 63.4% had experienced UI more than once a month during the prior 12 months. Among the respondents, 36.6% had no UI, 47.5% had stress UI, 0.4% had urge UI, and 15.5% had mixed UI. The mean LUTS score of the total respondents was 7.8 +/- 4.1. The LUTS was significantly predicted by age (p < .0001) and mixed UI (p < .0001), and 79.4% of variance in LUTS was explained. The highest LUTS scores were shown in the subjects with mixed UI, and we found that LUTS scores increased with age.

Adult↗

PubMed2005

H2B (Ser10) phosphorylation is induced during apoptosis and meiosis in S. cerevisiae.

The nucleosome, composed of an octamer of highly conserved histone proteins and associated DNA, is the fundamental unit of eukaryotic chromatin. How arrays of nucleosomes are folded into higher-order structures, and how the dynamics of such compaction are regulated, are questions that remain largely unanswered. Our recent studies demonstrated that phosphorylation of histone H2B is necessary to induce cell death that exhibits phenotypic hallmarks of apoptosis including DNA fragmentation and chromatin condensation in yeast (serine 10)1 and in mammalian cells (serine 14)2. In this article, we extend these findings by uncovering a role for H2B phosphorylation at serine 10 (Ser10) in another biological event that is associated with dramatic alterations in higher-order chromatin structure, meiosis. Our data show strong staining, indicative of H2B (Ser10) phosphorylation, during the pachytene stage of yeast meiotic prophase. These data broaden the use of this phosphorylation mark in chromatin remodeling that closely correlates with chromatin compaction. How phosphorylation marks are translated into meaningful downstream events during processes as diverse as apoptosis and meiosis remain a challenge for future studies.

Animals↗

PubMed2005

Phosphorylation of histone H4 serine 1 during DNA damage requires casein kinase II in S. cerevisiae.

Distinct patterns of posttranslational histone modifications can regulate DNA-templated events such as mitosis, transcription, replication, apoptosis, and DNA damage, suggesting the presence of a "histone code" in these nuclear processes. Phosphorylation of histone H2A S129 at sites of DNA double-strand breaks (DSBs) has been implicated in damage repair in yeast. Here, we describe another phosphorylation event on serine 1 (S1) of histone H4; this event is also associated with MMS- or phleomycin-induced DSBs but not with UV-induced DNA damage. Chromatin-immunoprecipitation (ChIP) studies of an HO-endonuclease-inducible strain show that S1 phosphorylation is specifically enhanced 20- to 25-fold in nucleosomes proximal to the DSB. In addition, we show that casein kinase II (CK2) can phosphorylate H4 S1 in vitro and that null or temperature-sensitive CK2 yeast mutants are defective for induction of H4 S1 phosphorylation upon DNA damage in vivo. Furthermore, H4 S1 phosphorylation and CK2 play a role in DSB re-joining as indicated by a nonhomologous end-joining (NHEJ) plasmid assay. CK2 has been implicated in regulating a DNA-damage response; our data suggest that histone H4 S1 is one of its physiological substrates. These data suggest that this modification is a part of the DNA-repair histone code.

Blotting, Western↗

PubMed2005

Sterile 20 kinase phosphorylates histone H2B at serine 10 during hydrogen peroxide-induced apoptosis in S. cerevisiae.

Apoptosis is a highly coordinated cell suicide mechanism in vertebrates. Phosphorylation of serine 14 of histone H2B, catalyzed by Mst1 kinase, has been linked to chromatin compaction during apoptosis. We extend these results to unicellular eukaryotes by demonstrating that H2B is specifically phosphorylated at serine 10 (S10) in a hydrogen peroxide-induced cell death pathway in S. cerevisiae. H2B S10A mutants are resistant to cell death elicited by H(2)O(2) while H2B S10E phospho-site mimics promote cell death and induce the "constitutive" formation of condensed chromatin. Ste20 kinase, a yeast homolog of mammalian Mst1 kinase, translocates into the nucleus in a caspase-independent fashion and directly phosphorylates H2B at S10. Conservation of targeted H2B phosphorylation and the enzyme system responsible for the process point to an ancient mechanism of chromatin remodeling that likely plays an important role in governing cellular homeostasis in a wide range of organisms.

Apoptosis↗

PubMed2003

Korean nursing students' ethical problems and ethical decision making.

This Korean study replicated a previously published American study. The conceptual framework and method combined ethical enquiry and phenomenology. The research questions were: (1) What is nursing students' experience of ethical problems involving nursing practice? and, (2) What is nursing students' experience of using an ethical decision-making model? The participants were 97 senior baccalaureate nursing students, each of whom described one ethical problem and chose to use one of five ethical decision-making models. From 97 ethical problems, five content categories emerged, the largest being health professionals (69%). The basic nature of the ethical problems was the students' experience of conflict, resolution and rationale. Using an ethical decision-making model helped 94% of the students. A comparison of the Korean and American results yields important implications for nursing ethics education, practice and research.

Adult↗

PubMedDate not supplied

Impact of a nurse short message service intervention for patients with diabetes.

The purpose of this study was to investigate the effect of a nurse short message service by cellular phone and the Internet on glycosylated hemoglobin (HbA1c) levels and adherence to diabetes control recommendations. The patients with diabetes were asked to input their blood glucose levels every day by cellular phone or the Internet. Optimal recommendations were sent weekly to each patient by short message service. After 12 weeks, the patients had a mean decrease of 1.1% in HbA1c level and an increase in diabetic medication taking, 30 minutes of physical exercise, and foot care adherence.

Adult↗