KERATINS AND SKIN DISORDERS

The epidermal keratinocytes express two major pairs of keratin polypeptides. One pair (K5/K14) expressed specifically in basal generative compartment and the other (K1/K10) expressed specifically in the differentiating suprabasal compartment. The switch in the expression of the keratins from proliferating to differentiating compartment indicates the changes that occur in the keratin filament organization which in turn influences the functional properties of the epidermis. Proper regulation of keratin gene expression and the filament organization are absolutely necessary for normal functioning of the skin. Keratin gene mutations can influence the filament integrity thereby causing several heritable blistering disorders of the skin such as epidermolysis bullosa, bullous icthyosiform erythroderma, etc. Changes in the keratin gene expression may lead to incomplete differentiation of the epidermal keratinocyte, causing hyperproliferative diseases of the skin such as psoriasis, carcinomas, etc. This review briefly describes the changes in keratin structure or gene expression that are known to result in various disorders of the skin.     

Bacteriophage adenine methyltransferase: a life cycle regulator? Modelled using Vibrio harveyi myovirus like

The adenine methyltransferase (DAM) gene methylates GATC sequences that have been demonstrated in various bacteria to be a powerful gene regulator functioning as an epigenetic switch, particularly with virulence gene regulation. However, overproduction of DAM can lead to mutations, giving rise to variability that may be important for adaptation to environmental change. While most bacterial hosts carry a DAM gene, not all bacteriophage carry this gene. Currently, there is no literature regarding the role DAM plays in life cycle regulation of bacteriophage. Vibrio campbellii strain 642 carries the bacteriophage Vibrio harveyi myovirus like (VHML) that has been proven to increase virulence. The complete genome sequence of VHML bacteriophage revealed a putative adenine methyltransferase gene. Using VHML, a new model of phage life cycle regulation, where DAM plays a central role between the lysogenic and lytic states, will be hypothesized. In short, DAM methylates the rha antirepressor gene and once methylation is removed, homologous CI repressor protein becomes repressed and non‐functional leading to the switching to the lytic cycle. Greater understanding of life cycle regulation at the genetic level can, in the future, lead to the genesis of chimeric bacteriophage with greater control over their life cycle for their safe use as probiotics within the aquaculture industry.     

Mental illness and well‐being: an affect regulation perspective

Mental health crucially depends upon affective states such as emotions, stress responses, impulses and moods. These states shape how we think, feel and behave. Often, they support adaptive functioning. At other times, however, they can become detrimental to mental health via maladaptive affect generation processes and/or maladaptive affect regulation processes. Here, we present an integrative framework for considering the role of affect generation and regulation in mental illness and well‐being. Our model views affect generation as an iterative cycle of attending to, appraising and responding to situations. It views affect regulation as an iterative series of decisions aimed at altering affect generation. Affect regulation decisions include identifying what, if anything, should be changed about affect, selecting where to intervene in the affect generation cycle, choosing how to implement this intervention, and monitoring the regulation attempt to decide whether to maintain, switch or stop it. Difficulties with these decisions, often arising from biased inputs to them, can contribute to manifestations of mental illness such as clinical symptoms, syndromes and disorders. The model has a number of implications for clinical assessment and treatment. Specifically, it offers a common set of concepts for characterizing different affective states; it highlights interactions between affect generation and affect regulation; it identifies assessment and treatment targets among the component processes of affect regulation; and it is applicable to prevention and treatment of mental illness as well as to promotion and restoration of psychological well‐being.     

Bacteriophage lambda: the untold story.

The study of bacteriophage lambda has provided key insights into fundamental biological processes. This review recalls some highlights in the history of lambda research, and relates how simple (but elegant) experiments yielded major scientific breakthroughs. What we know about recombination, gene regulation, and protein folding, for example, derives in large part from bacteriophage lambda genetics. Lambda not only represents a model system of scientific logic in a technology-driven age, but continues to reveal new principles of molecular biology.     

Applications of EcR gene switch technology in functional genomics

Genetic engineering of plants using transgenic technology is targeted to enhance agronomic performance or improved quality traits in a wide variety of plant species, and has become a fundamental tool for basic research in plant biotechnology. Constitutive promoters are presently the primary means used to express transgenes in plants. However, inducible gene regulation systems based on specific chemicals have many potential applications in agriculture and for enhancing the basic understanding of gene function. As a result, several gene switches have been developed. The ecdysone receptor gene switch is one of the best inducible gene regulation systems available, because the chemical, methoxyfenozide, required for its regulation is registered for field use. An EcR gene switch with a potential for use in large-scale field applications has been developed by adopting a two-hybrid format. In a two-hybrid switch format, the GAL4 DNA binding domain (GAL4 DBD) was fused to the ligand binding domain (LBD) of the Choristoneura fumiferana ecdysone receptor (CfEcR); and, the VP16 activation domain (VP16 AD) was fused to the LBD of Locust migratoria retinoid X receptor (LmRXR). The sensitivity of the CfEcR gene switch was improved from micromolar to nanomolar concentrations of ligand by using the CfEcR:LmRXR two-hybrid switch. In this report, we demonstrate the utility of CfEcR:LmRXR two-hybrid gene switch in functional genomics applications for regulating the expression of a Superman-like single zinc finger protein 11 (ZFP11) gene in both Arabidopsis and tobacco transgenic plants.     

LsrR quorum sensing "switch" is revealed by a bottom-up approach

Quorum sensing (QS) enables bacterial multicellularity and selective advantage for communicating populations. While genetic "switching" phenomena are a common feature, their mechanistic underpinnings have remained elusive. The interplay between circuit components and their regulation are intertwined and embedded. Observable phenotypes are complex and context dependent. We employed a combination of experimental work and mathematical models to decipher network connectivity and signal transduction in the autoinducer-2 (AI-2) quorum sensing system of E. coli. Negative and positive feedback mechanisms were examined by separating the network architecture into sub-networks. A new unreported negative feedback interaction was hypothesized and tested via a simple mathematical model. Also, the importance of the LsrR regulator and its determinant role in the E. coli QS "switch", normally masked by interfering regulatory loops, were revealed. Our simple model allowed mechanistic understanding of the interplay among regulatory sub-structures and their contributions to the overall native functioning network. This "bottom up" approach in understanding gene regulation will serve to unravel complex QS network architectures and lead to the directed coordination of emergent behaviors.     

Development of a tightly regulated and highly inducible ecdysone receptor gene switch for plants through the use of retinoid X receptor chimeras

Chemical inducible gene regulation systems provide essential tools for the precise regulation of transgene expression in plants and animals. Recent development of a two-hybrid ecdysone receptor (EcR) gene regulation system has solved some of the drawbacks that were associated with the monopartate gene switch. To further improve the versatility of the two-hybrid EcR gene switch for wide spread use in plants, chimeras between Homo sapiens retinoid X receptor (HsRXR) and insect, Locusta migratoria RXR (LmRXR) were tested in tobacco protoplasts as partners with Choristoneura fumiferana EcR (CfEcR) in inducing expression of the luciferase reporter gene. The RXR chimera 9 (CH9) along with CfEcR, in a two-hybrid format gave the best results in terms of low-background expression levels in the absence of ligand and high-induced expression levels of the reporter gene in the presence of nanomolar concentrations of the methoxyfenozide ligand. The performance of CH9 was further tested in corn and soybean protoplasts and the data obtained was compared with the other EcR switches that contained the wild-type LmRXR or HsRXR as EcR partners. In both transient expression studies and stable transformation experiments, the fold induction values obtained with the CH9 switch were several times higher than the values obtained with the other EcR switches containing LmRXR or HsRXR. The new CfEcR two-hybrid gene switch that uses the RXR CH9 as a partner in inducing reporter gene expression provides an efficient, ligand-sensitive and tightly regulated gene switch for plants.     

Inheritance and state switching of genetic toggle switch in different culture growth phases

Using the gene engineering methods, one can construct simple artificial gene networks with two stable functioning regimes (bistable genetic systems). Such genetic systems make it possible for cells with identical genotype to inherit two alternative phenotypes. The toggle switch is just one of the types of bistable genetic systems. In this work, we investigate the inheritance and switching of toggle switch functioning regimes in the cells at different culture growth phases. It is shown that during transition into the stationary growth phase the inheritance of stable states is disturbed and variations in the toggle-switching rate are more possible in different cells. Also, simultaneous expression of two genes of the system has been experimentally modelled. According to our results, the culture growth phase in this period determines later on the ratio between cell phenotypes in a population.     

双报道基因系统的构建以及在N蛋白生物功能研究中的应用

为研究 λ噬菌体调控因子 Ｎ 蛋白的生物功能,应用 λ噬菌体感染、 Ｐ１ 噬菌体转导、体内、体外重组方法,通过对遗传标记的筛选,将 ｌａｃ Ｚ 和 ｇａｌ Ｋ 报道基因、λ噬菌体 ｐ Ｌ 操纵子负责调控转录、翻译的 Ｄ Ｎ Ａ 序列以及转录终止子装配到大肠杆菌染色体上,构建成菌株 Ｚ Ｈ１０４１、 Ｚ Ｈ１０４２ 和 Ｚ Ｈ１１４２．应用 Ｚ Ｈ１１４２ 菌株模拟 λ噬菌体的自然状态对其调控蛋白 Ｎ 的生物功能进行了研究．研究证明, Ｎ 蛋白不仅在转录水平上正向调控基因表达,还具有一种新的在翻译水平上负向调节自身基因表达的生物功能．