title: The Structure of the Oligomerization Domain of Lsr2 from Mycobacterium tuberculosis Reveals a Mechanism for Chromosome Organization and Protection

authors: Summers, Emma Louise

subjects: Science & Technology

abstract: Lsr2 is a small DNA-binding protein present in mycobacteria and related actinobacteria that regulates gene expression and influences the organization of bacterial chromatin. Lsr2 is a dimer that binds to AT-rich regions of chromosomal DNA and physically protects DNA from damage by reactive oxygen intermediates (ROI). A recent structure of the C-terminal DNAbinding domain of Lsr2 provides a rationale for its interaction with the minor groove of DNA, its preference for AT-rich tracts, and its similarity to other bacterial nucleoid-associated DNA-binding domains. In contrast, the details of Lsr2 dimerization (and oligomerization) via its N-terminal domain, and the mechanism of Lsr2-mediated chromosomal crosslinking and protection is unknown. We have solved the structure of the N-terminal domain of Lsr2 (N-Lsr2) at 1.73 A˚ resolution using crystallographic ab initio approaches. The structure shows an intimate dimer of two ß–ß–a motifs with no close homologues in the structural databases. The organization of individual N-Lsr2 dimers in the crystal also reveals a mechanism for oligomerization. Proteolytic removal of three N-terminal residues from Lsr2 results in the formation of an anti-parallel b-sheet between neighboring molecules and the formation of linear chains of N-Lsr2. Oligomerization can be artificially induced using low concentrations of trypsin and the arrangement of N-Lsr2 into long chains is observed in both monoclinic and hexagonal crystallographic space groups. In solution, oligomerization of N-Lsr2 is also observed following treatment with trypsin. A change in chromosomal topology after the addition of trypsin to full-length Lsr2-DNA complexes and protection of DNA towards DNAse digestion can be observed using electron microscopy and electrophoresis. These results suggest a mechanism for oligomerization of Lsr2 via protease-activation leading to chromosome compaction and protection, and concomitant down-regulation of large numbers of genes. This mechanism is likely to be relevant under conditions of stress where cellular proteases are known to be upregulated.

text: The Structure of the Oligomerization Domain of Lsr2 from Mycobacterium tuberculosis Reveals a Mechanism for Chromosome Organization and Protection Lsr2 is a small DNA-binding protein present in mycobacteria and related actinobacteria that regulates gene expression and influences the organization of bacterial chromatin. Lsr2 is a dimer that binds to AT-rich regions of chromosomal DNA and physically protects DNA from damage by reactive oxygen intermediates (ROI). A recent structure of the C-terminal DNAbinding domain of Lsr2 provides a rationale for its interaction with the minor groove of DNA, its preference for AT-rich tracts, and its similarity to other bacterial nucleoid-associated DNA-binding domains. In contrast, the details of Lsr2 dimerization (and oligomerization) via its N-terminal domain, and the mechanism of Lsr2-mediated chromosomal crosslinking and protection is unknown. We have solved the structure of the N-terminal domain of Lsr2 (N-Lsr2) at 1.73 A˚ resolution using crystallographic ab initio approaches. The structure shows an intimate dimer of two ß–ß–a motifs with no close homologues in the structural databases. The organization of individual N-Lsr2 dimers in the crystal also reveals a mechanism for oligomerization. Proteolytic removal of three N-terminal residues from Lsr2 results in the formation of an anti-parallel b-sheet between neighboring molecules and the formation of linear chains of N-Lsr2. Oligomerization can be artificially induced using low concentrations of trypsin and the arrangement of N-Lsr2 into long chains is observed in both monoclinic and hexagonal crystallographic space groups. In solution, oligomerization of N-Lsr2 is also observed following treatment with trypsin. A change in chromosomal topology after the addition of trypsin to full-length Lsr2-DNA complexes and protection of DNA towards DNAse digestion can be observed using electron microscopy and electrophoresis. These results suggest a mechanism for oligomerization of Lsr2 via protease-activation leading to chromosome compaction and protection, and concomitant down-regulation of large numbers of genes. This mechanism is likely to be relevant under conditions of stress where cellular proteases are known to be upregulated.

year: 2012-06-13

title: University Students' Knowledge of and Attitudes toward Sex Offenders and Treatment of Sex Offenders in New Zealand and China

authors: Liu, Sen

subjects: attitudes

abstract: Topics related to sexual offending and sex offenders can provoke a great deal of fear and anxiety in society. Sex offenders are a group of people who are considered to be especially unpleasant and harmful compared to other types of offenders. Over the past two decades, academic researchers and clinical professionals have developed a variety of assessment methods and treatment programmes to reduce recidivism rates of sex offenders. Public attitudes toward sex offenders are proposed to play an important role in the effectiveness of treatment for sex offenders. Thus, general community members’ attitudes have been widely studied in western countries. However, there is little cross-cultural research exploring Asian people’s attitudes toward sex offenders. The three keys purposes of this study were to examine university students’ knowledge of and attitudes toward sex offenders, explore how their knowledge and attitudes were formed, and compare the similarities and differences between New Zealand and Chinese university students. A total of 62 participants were included in this study; 29 from New Zealand and 33 from China. It was hypothesized that New Zealand university students would be more knowledgeable of and positive toward sex offenders, treatment of sex offenders and released sex offenders than Chinese university students. The results supported hypotheses that New Zealand students had greater knowledge of and positive attitudes toward sex offenders and treatment of sex offenders. However, no difference was found in people’s attitudes toward released sex offenders between two groups of students. The results also indicated that the news media was the most common source of information on sexual offending and sex offenders in both countries. However, there is a great difference in people’s attitudes toward veracity of information provided by the media between New Zealand and Chinese students. The results are considered in light of current research. Implications and future research directions are briefly discussed.

text: University Students' Knowledge of and Attitudes toward Sex Offenders and Treatment of Sex Offenders in New Zealand and China Topics related to sexual offending and sex offenders can provoke a great deal of fear and anxiety in society. Sex offenders are a group of people who are considered to be especially unpleasant and harmful compared to other types of offenders. Over the past two decades, academic researchers and clinical professionals have developed a variety of assessment methods and treatment programmes to reduce recidivism rates of sex offenders. Public attitudes toward sex offenders are proposed to play an important role in the effectiveness of treatment for sex offenders. Thus, general community members’ attitudes have been widely studied in western countries. However, there is little cross-cultural research exploring Asian people’s attitudes toward sex offenders. The three keys purposes of this study were to examine university students’ knowledge of and attitudes toward sex offenders, explore how their knowledge and attitudes were formed, and compare the similarities and differences between New Zealand and Chinese university students. A total of 62 participants were included in this study; 29 from New Zealand and 33 from China. It was hypothesized that New Zealand university students would be more knowledgeable of and positive toward sex offenders, treatment of sex offenders and released sex offenders than Chinese university students. The results supported hypotheses that New Zealand students had greater knowledge of and positive attitudes toward sex offenders and treatment of sex offenders. However, no difference was found in people’s attitudes toward released sex offenders between two groups of students. The results also indicated that the news media was the most common source of information on sexual offending and sex offenders in both countries. However, there is a great difference in people’s attitudes toward veracity of information provided by the media between New Zealand and Chinese students. The results are considered in light of current research. Implications and future research directions are briefly discussed.

year: 2014

title: Invading the Waikato: A postcolonial re-view

authors: Dench, Simon

subjects: New Zealand

abstract: The article discusses images of the Waikato Region of New Zealand from the 1860s, examining them within the context of British colonization and invasion. It comments on photographs by surveyor Daniel Manders Beere and British Army Royal Artillery Regiment Assistant Surgeon William Temple. The author also comments on a map of New Zealand's North Island made by surveyor Charles Heaphy and a map of Newcastle, New Zealand, depicting its earlier names of Ngāruawāhia and Queenstown. Other topics include spatial history, postcolonialism, and the 1863 to 1864 British invasion of Waikato.

text: Invading the Waikato: A postcolonial re-view The article discusses images of the Waikato Region of New Zealand from the 1860s, examining them within the context of British colonization and invasion. It comments on photographs by surveyor Daniel Manders Beere and British Army Royal Artillery Regiment Assistant Surgeon William Temple. The author also comments on a map of New Zealand's North Island made by surveyor Charles Heaphy and a map of Newcastle, New Zealand, depicting its earlier names of Ngāruawāhia and Queenstown. Other topics include spatial history, postcolonialism, and the 1863 to 1864 British invasion of Waikato.

year: 2011