A proline-rich region in the Zeste protein essential for transvection and white repression by Zeste

Matrix analysis of the digital divide in eHealth services using awareness, want, and adoption gap

Background

The digital divide usually refers to access or usage, but some studies have identified two other divides: awareness and demand (want). Given that the hierarchical stages of the innovation adoption process of a customer are interrelated, it is necessary and meaningful to analyze the digital divide in eHealth services through three main stages, namely, awareness, want, and adoption.

Objective

By following the three main integrated stages of the innovation diffusion theory, from the customer segment viewpoint, this study aimed to propose a new matrix analysis of the digital divide using the awareness, want, and adoption gap ratio (AWAG). I compared the digital divide among different groups. Furthermore, I conducted an empirical study on eHealth services to present the practicability of the proposed methodology.

Methods

Through a review and discussion of the literature, I proposed hypotheses and a new matrix analysis. To test the proposed method, 3074 Taiwanese respondents, aged 15 years and older, were surveyed by telephone. I used the stratified simple random sampling method, with sample size allocation proportioned by the population distribution of 23 cities and counties (strata).

Results

This study proposed the AWAG segment matrix to analyze the digital divide in eHealth services. First, awareness and want rates were divided into two levels at the middle point of 50%, and then the 2-dimensional cross of the awareness and want segment matrix was divided into four categories: opened group, desire-deficiency group, perception-deficiency group, and closed group. Second, according to the degrees of awareness and want, each category was further divided into four subcategories. I also defined four possible strategies, namely, hold, improve, evaluate, and leave, for different regions in the proposed matrix. An empirical test on two recently promoted eHealth services, the digital medical service (DMS) and the digital home care service (DHCS), was conducted. Results showed that for both eHealth services, the digital divides of awareness, want, and adoption existed across demographic variables, as well as between computer owners and nonowners, and between Internet users and nonusers. With respect to the analysis of the AWAG segment matrix for DMS, most of the segments, except for people with marriage status of Other or without computers, were positioned in the opened group. With respect to DHCS, segments were separately positioned in the opened, perception-deficiency, and closed groups.

Conclusions

Adoption does not closely follow people’s awareness or want, and a huge digital divide in adoption exists in DHS and DHCS. Thus, a strategy to promote adoption should be used for most demographic segments.

The awareness and want matrix with adoption gap ratio analysis for e-service diffusion effect

Since the hierarchical stages of a customer purchasing decision or innovation adoption process are interrelated, an analysis of all their stages, including awareness, want, and adoption, in relation to product or service diffusion, is urgently needed. Therefore, this study proposes the use of an awareness and want matrix, together with an adoption gap ratio analysis, to assess the effectiveness of innovation and technology diffusion for e-services. This study also conducts an empirical test on the promotion performance evaluation of 12 e-services promoted by the Taiwanese government.

Molecular genetic analysis of Suppressor 2 of zeste identifies key functional domains

The Su(z)2 complex contains Posterior sex combs (Psc) and Suppressor 2 of zeste [Su(z)2], two paralogous genes that likely arose by gene duplication. Psc encodes a Polycomb group protein that functions as a central component of the PRC1 complex, which maintains transcriptional repression of a wide array of genes. Although much is known about Psc, very little is known about Su(z)2, the analysis of which has been hampered by a dearth of alleles. We have generated new alleles of Su(z)2 and analyzed them at the genetic and molecular levels. Some of these alleles display negative complementation in that they cause lethality when heterozygous with the gain-of-function Su(z)2(1) allele but are hemizygous and, in some cases, homozygous viable. Interestingly, alleles of this class identify protein domains within Su(z)2 that are highly conserved in Psc and the mammalian Bmi-1 and Mel-18 proteins. We also find several domains of intrinsic disorder in the C-terminal regions of both Psc and Su(z)2 and suggest that these domains may contribute to the essential functions of both proteins.

Regulation of Polycomb group complexes by the sequence-specific DNA binding proteins Zeste and GAGA

Repression and activation of the expression of homeotic genes are maintained by proteins encoded by the Polycomb group (PcG) and trithorax group (trxG) genes. Complexes formed by these proteins are targeted by PcG or trxG response elements (PREs/TREs), which share binding sites for several of the same factors. GAGA factor and Zeste bind specifically to PREs/TREs and have been shown to act as both activators and repressors. We have used purified proteins and complexes reconstituted from recombinant subunits to characterize the effects of GAGA and Zeste proteins on PcG function using a defined in vitro system. Zeste directly associates with the PRC1 core complex (PCC) and enhances the inhibitory activity of this complex on all templates, with a preference for templates with Zeste binding sites. GAGA does not stably associate with PCC, but nucleosomal templates bound by GAGA are more efficiently bound and more efficiently inhibited by PCC. Thus Zeste and GAGA factor use distinct means to increase repression mediated by PRC1.

Characterization of the extended Myb-like DNA-binding domain of trithorax group protein Zeste

Zeste is a Drosophila sequence-specific DNA-binding protein that performs a variety of functions during chromatin-directed gene regulation. Its DNA-binding domain (DBD) was previously identified, but no similarities to established DNA-binding structures are known. Here we present sequence comparisons suggesting that the Zeste-DBD is a novel variant of the tri-helical Myb-DBD. Using band shift assays, we mapped the Zeste-DBD to 76 residues, corresponding to a single Myb repeat of only 50 residues. All residues involved in formation of the hydrophobic core of the Myb domain are conserved in Zeste, suggesting it forms an extended Myb domain. Mutagenesis studies determined (T/C/g)GAGTG(A/G/c) as the consensus Zeste recognition sequence. Reconstituted transcription experiments established that deviations from this optimal consensus compromise transcriptional activation by Zeste. In addition, flanking DNA is critical because Zeste-DBD binding requires a DNA sequence of minimally 16 base pairs, which is much longer than the consensus site. The DNA flanking the consensus is contacted by Zeste through sequence-independent backbone contacts. Interestingly, hydroxyl radical footprinting revealed that the Zeste-DNA backbone contacts all map to one face of the DNA. We compare the DNA-binding properties of Zeste with those of classical tri-helical DBDs harboring a helix-turn-helix motif and suggest a model for Zeste-DNA recognition.

Chromatin silencing and activation by Polycomb and trithorax group proteins

The Polycomb group (PcG) of repressors and the trithorax group (trxG) of activators maintain the correct expression of several key developmental regulators, including the homeotic genes. PcG and trxG proteins function in distinct multiprotein complexes that are believed to control transcription by changing the structure of chromatin, organizing it into either a 'closed' or an 'open' conformation. The hallmark of gene regulation by PcG/trxG proteins is that it can lead to a mitotically stable pattern of gene expression, often referred to as epigenetic regulation. Although much remains to be learned, recent studies have provided insights into how this epigenetic switch is set, how PcG/trxG proteins might be linked to cis-acting DNA elements and what potential mechanisms underlie stable inheritance of gene expression status over multiple cell divisions. Finally, the study of the evolutionarily conserved PcG/trxG factors has recently gained additional urgency with the realization that they play a pertinent role in certain human cancers.

A screen for new trithorax group genes identified little imaginal discs, the Drosophila melanogaster homologue of human retinoblastoma binding protein 2

The proteins encoded by two groups of conserved genes, the Polycomb and trithorax groups, have been proposed to maintain, at the level of chromatin structure, the expression pattern of homeotic genes during Drosophila development. To identify new members of the trithorax group, we screened a collection of deficiencies for intergenic noncomplementation with a mutation in ash1, a trithorax group gene. Five of the noncomplementing deletions uncover genes previously classified as members of the Polycomb group. This evidence suggests that there are actually three groups of genes that maintain the expression pattern of homeotic genes during Drosophila development. The products of the third group appear to be required to maintain chromatin in both transcriptionally inactive and active states. Six of the noncomplementing deficiencies uncover previously unidentified trithorax group genes. One of these deficiencies removes 25D2-3 to 26B2-5. Within this region, there are two, allelic, lethal P-insertion mutations that identify one of these new trithorax group genes. The gene has been called little imaginal discs based on the phenotype of mutant larvae. The protein encoded by the little imaginal discs gene is the Drosophila homologue of human retinoblastoma binding protein 2.

The Drosophila Brahma complex is an essential coactivator for the trithorax group protein Zeste

The trithorax group (trxG) of activators andPolycomb group (PcG) of repressors are believed to control the expression of several key developmental regulators by changing the structure of chromatin. Here, we have sought to dissect the requirements for transcriptional activation by the DrosophilatrxG protein Zeste, a DNA-binding activator of homeotic genes. Reconstituted transcription reactions established that the Brahma (BRM) chromatin-remodeling complex is essential for Zeste-directed activation on nucleosomal templates. Because it is not required for Zeste to bind to chromatin, the BRM complex appears to act after promoter binding by the activator. Purification of the Drosophila BRM complex revealed a number of novel subunits. We found that Zeste tethers the BRM complex via direct binding to specific subunits, including trxG proteins Moira (MOR) and OSA. The leucine zipper of Zeste mediates binding to MOR. Interestingly, although the Imitation Switch (ISWI) remodelers are potent nucleosome spacing factors, they are dispensable for transcriptional activation by Zeste. Thus, there is a distinction between general chromatin restructuring and transcriptional coactivation by remodelers. These results establish that different chromatin remodeling factors display distinct functional properties and provide novel insights into the mechanism of their targeting.

The Drosophila brahma complex is an essential coactivator for the trithorax group protein zeste

The trithorax group (trxG) of activators and Polycomb group (PcG) of repressors are believed to control the expression of several key developmental regulators by changing the structure of chromatin. Here, we have sought to dissect the requirements for transcriptional activation by the Drosophila trxG protein Zeste, a DNA-binding activator of homeotic genes. Reconstituted transcription reactions established that the Brahma (BRM) chromatin-remodeling complex is essential for Zeste-directed activation on nucleosomal templates. Because it is not required for Zeste to bind to chromatin, the BRM complex appears to act after promoter binding by the activator. Purification of the Drosophila BRM complex revealed a number of novel subunits. We found that Zeste tethers the BRM complex via direct binding to specific subunits, including trxG proteins Moira (MOR) and OSA. The leucine zipper of Zeste mediates binding to MOR. Interestingly, although the Imitation Switch (ISWI) remodelers are potent nucleosome spacing factors, they are dispensable for transcriptional activation by Zeste. Thus, there is a distinction between general chromatin restructuring and transcriptional coactivation by remodelers. These results establish that different chromatin remodeling factors display distinct functional properties and provide novel insights into the mechanism of their targeting.

Distant liaisons: long-range enhancer-promoter interactions in Drosophila

Transcriptional activation of many developmentally regulated genes is mediated by proteins binding to enhancer sequences located several kilobases from the promoter. Existing models for how activator proteins function do not adequately explain long-range activation. Recent experiments in Drosophila on insulators that block enhancer-promoter interactions, interchromosomal activation, and mutants deficient in long-range activation are consistent with models in which facilitator factors that function between enhancers and promoters bring them into physical proximity of each other.

Transvection and other homology effects

The presence of homologous nucleic acid sequences can exert profound effects on chromosomal and gene function in a wide range of organisms. These homology effects reveal remarkable forms of regulation as well as suggest possible avenues for the development of new technologies.