title: The Biochemistry of VapBC Toxin-Antitoxins

authors: McKenzie, Joanna Leigh

subjects: Biochemistry

abstract: The VapBC toxin-antitoxin (TA) systems were first identified in 2005 and little is known about their contemporary biological function, despite the fact that VapBC TAs are the largest TA family and are widespread in bacteria and archaea (Arcus, Rainey, & Turner, 2005; Gerdes, Christensen, & Lobner-Olsen, 2005). Mycobacterium tuberculosis has a surprisingly large repertoire of 45 VapBC TAs. In contrast Mycobacterium smegmatis, a model organism for M. tuberculosis, contains only one vapBC operon, thereby making it an ideal system to uncover the possible role(s) that VapBC proteins play in mycobacteria. This thesis describes the functional characterisation of VapC from M. smegmatis and two homologues from Pyrobaculum aerophilum, along with biophysical characterisation of the VapBC complex from M. smegmatis. The VapBC proteins from M. smegmatis form a tight complex in a 1:1 ratio and interactions between the proteins result in a tetramer of VapBC heterodimers. VapB is susceptible to proteolytic degradation when not bound to DNA thus hinting at a mechanism for VapC activation.
VapC proteins from P. aerophilum (VapCPAE2754 and VapCPAE0151) and VapC from M. smegmatis display Mg²⁺/Mn²⁺ dependent, sequence specific ribonuclease activity. VapC from M. smegmatis targets the AU rich sequences AUAU and AUAA. Whereas VapCPAE2754 and VapCPAE0151 from P. aerophilum both target GGUG and GGGG sequences. These sequences are present in over half the mRNA transcripts encoded in the P. aerophilum genome, making them potent toxins. VapC ribonuclease activity is inhibited when VapC is bound to VapB. When VapC is released from the VapBC complex it cleaves cohorts of mRNA transcripts thereby reducing protein synthesis for this cohort of genes. Microarray analysis revealed that the majority of transcripts downregulated in response to VapC expression in M. smegmatis are involved in carbon utilisation and transport (Robson, 2010). Bioinformatics shows that the target sequence is overrepresented in the downregulated transcripts. The majority of the downregulated genes are in operons, which suggests a mechanism for destabilising mRNA transcripts to regulate specific metabolic processes.

text: The Biochemistry of VapBC Toxin-Antitoxins The VapBC toxin-antitoxin (TA) systems were first identified in 2005 and little is known about their contemporary biological function, despite the fact that VapBC TAs are the largest TA family and are widespread in bacteria and archaea (Arcus, Rainey, & Turner, 2005; Gerdes, Christensen, & Lobner-Olsen, 2005). Mycobacterium tuberculosis has a surprisingly large repertoire of 45 VapBC TAs. In contrast Mycobacterium smegmatis, a model organism for M. tuberculosis, contains only one vapBC operon, thereby making it an ideal system to uncover the possible role(s) that VapBC proteins play in mycobacteria. This thesis describes the functional characterisation of VapC from M. smegmatis and two homologues from Pyrobaculum aerophilum, along with biophysical characterisation of the VapBC complex from M. smegmatis. The VapBC proteins from M. smegmatis form a tight complex in a 1:1 ratio and interactions between the proteins result in a tetramer of VapBC heterodimers. VapB is susceptible to proteolytic degradation when not bound to DNA thus hinting at a mechanism for VapC activation.
VapC proteins from P. aerophilum (VapCPAE2754 and VapCPAE0151) and VapC from M. smegmatis display Mg²⁺/Mn²⁺ dependent, sequence specific ribonuclease activity. VapC from M. smegmatis targets the AU rich sequences AUAU and AUAA. Whereas VapCPAE2754 and VapCPAE0151 from P. aerophilum both target GGUG and GGGG sequences. These sequences are present in over half the mRNA transcripts encoded in the P. aerophilum genome, making them potent toxins. VapC ribonuclease activity is inhibited when VapC is bound to VapB. When VapC is released from the VapBC complex it cleaves cohorts of mRNA transcripts thereby reducing protein synthesis for this cohort of genes. Microarray analysis revealed that the majority of transcripts downregulated in response to VapC expression in M. smegmatis are involved in carbon utilisation and transport (Robson, 2010). Bioinformatics shows that the target sequence is overrepresented in the downregulated transcripts. The majority of the downregulated genes are in operons, which suggests a mechanism for destabilising mRNA transcripts to regulate specific metabolic processes.

year: 2011

title: Charming or harming: Case studies of emotional abuse in heterosexual intimate partner relationships

authors: Corbett, Catherine

subjects: Emotional abuse

abstract: Emotional abuse in the absence of physical abuse is often unrecognised. Although the literature identifies the insidious nature of this type of abuse and the physiological, psychological and emotional harm it often causes, knowledge of how women come to recognise they are being emotionally abused is underdeveloped.
In response to this, the purpose of this research was to investigate the dynamics of emotionally abusive heterosexual intimate partner relationships and establish how women came to recognise their relationship as such. Four women who identified as having been emotionally abused by their male partner each took part in two in-depth semi-structured interviews about their experiences. The analysis and methodology of the research was underpinned by a feminist framework.
The interviews are presented in case study form, showing in context the undermining effects of the abuse and any difficulties the women faced in pinpointing what was so wrong with their relationships. 
Gender socialisation, myths surrounding abuse, and mixed messages from potential support systems, all influenced recognition. Theories useful for disentangling the complex social structure which may support emotional abuse of women included gender theories from Goffman and Connell, relational theory, and total institution theory among others.
The research highlights the importance of rethinking the nature of abuse from individual explosive acts of violence perpetrated by a certain type of person, to a continual process of more subtle undermining factors which are underpinned by patriarchy and gender inequality. For a more comprehensive picture of emotional abuse it becomes clear there is a need to step away from conceptualising it in a similar manner to physical abuse and to look not only in terms of acts done, but also in terms of reciprocity and neglect.

text: Charming or harming: Case studies of emotional abuse in heterosexual intimate partner relationships Emotional abuse in the absence of physical abuse is often unrecognised. Although the literature identifies the insidious nature of this type of abuse and the physiological, psychological and emotional harm it often causes, knowledge of how women come to recognise they are being emotionally abused is underdeveloped.
In response to this, the purpose of this research was to investigate the dynamics of emotionally abusive heterosexual intimate partner relationships and establish how women came to recognise their relationship as such. Four women who identified as having been emotionally abused by their male partner each took part in two in-depth semi-structured interviews about their experiences. The analysis and methodology of the research was underpinned by a feminist framework.
The interviews are presented in case study form, showing in context the undermining effects of the abuse and any difficulties the women faced in pinpointing what was so wrong with their relationships. 
Gender socialisation, myths surrounding abuse, and mixed messages from potential support systems, all influenced recognition. Theories useful for disentangling the complex social structure which may support emotional abuse of women included gender theories from Goffman and Connell, relational theory, and total institution theory among others.
The research highlights the importance of rethinking the nature of abuse from individual explosive acts of violence perpetrated by a certain type of person, to a continual process of more subtle undermining factors which are underpinned by patriarchy and gender inequality. For a more comprehensive picture of emotional abuse it becomes clear there is a need to step away from conceptualising it in a similar manner to physical abuse and to look not only in terms of acts done, but also in terms of reciprocity and neglect.

year: 2013

title: Impact of tephra fall and environmental change: a 1000 year record from Matakana Island, Bay of Plenty, North Island, New Zealand.

authors: Giles, Teresa M.

abstract: Palynological evidence was used to determine the development of vegetation communities on Matakana Island, North Island, New Zealand, over the last 1000 radiocarbon years. The pollen record indicates that changes occurred in the vegetation immediately following fallout deposition of the Kaharoa Tephra approximately 100 km from source at c. 665 years BP. Such changes may be a direct response to the impact of tephra fall, although the possibility of anthropogenic disturbance cannot be discounted. As a result of the eruption some taxa (Leucopogon fasciculatus and Tupeia antarctica) became at least temporarily extinct from the area. Two phases of anthropogenic influence on the environment are recorded in the pollen record: Polynesian, followed by European inhabitation of the island, giving a detailed history of human influence in the area for the millennium.

text: Impact of tephra fall and environmental change: a 1000 year record from Matakana Island, Bay of Plenty, North Island, New Zealand. Palynological evidence was used to determine the development of vegetation communities on Matakana Island, North Island, New Zealand, over the last 1000 radiocarbon years. The pollen record indicates that changes occurred in the vegetation immediately following fallout deposition of the Kaharoa Tephra approximately 100 km from source at c. 665 years BP. Such changes may be a direct response to the impact of tephra fall, although the possibility of anthropogenic disturbance cannot be discounted. As a result of the eruption some taxa (Leucopogon fasciculatus and Tupeia antarctica) became at least temporarily extinct from the area. Two phases of anthropogenic influence on the environment are recorded in the pollen record: Polynesian, followed by European inhabitation of the island, giving a detailed history of human influence in the area for the millennium.

year: 1999-01-01