This article investigates three teachers' conceptions and use of inquiry-based instructional strategies throughout a professional development program. The professional development program consisted of a 2-week summer inquiry institute and research experience in university scientists' laboratories, as well as three academic year workshops. Insights gained from an in-depth study of these three secondary teachers resulted in a model of teacher conceptions that can be used to direct future inquiry professional development. Teachers' conceptions of inquiry teaching were established through intensive case-study research that incorporated extensive classroom observations and interviews. Through their participation in the professional development experience, the teachers gained a deeper understanding of how to implement inquiry practices in their classrooms. The teachers gained confidence and practice with inquiry methods through developing and presenting their institute-developed inquiry lessons, through observing other teachers' lessons, and participating as students in the workshop inquiry activities. Data analysis revealed that a set of four core conceptions guided the teachers' use of inquiry-based practices in their classrooms. The teachers' conceptions of science, their students, effective teaching practices, and the purpose of education influenced the type and amount of inquiry instruction performed in the high school classrooms. The research findings suggest that to be successful inquiry professional development must not only teach inquiry knowledge, but it must also assess and address teachers' core teaching conceptions.
The heat shock transcription factor (HSF) is a trimer that binds to DNA containing inverted repeats of the sequence nGAAn. HSF can bind DNA with the sequence nGAAnnTTCn or with the sequence nTTCnnGAAn, with little preference for either sequence over the other. However, (nGAAnnTTCn)2 is considerably less active as a heat shock response element (HSE) than is (nTTCnnGAAn)2. The electrophoretic mobilities of DNA-protein complexes and chemical cross-linking between protein monomers indicate that the sequence (nGAAnnTTCn)2 is capable of binding a single HSF trimer. In contrast, the sequence with higher biological activity, (nTTCnnGAAn)2, is capable of binding two trimers. Thus, the ability of four-nGAAn-element HSEs to bind one or two trimers depends on the permutation with which the elements are presented. A survey of naturally occurring HSEs shows the sequence (nTTCnnGAAn)2 to be the more prevalent. We suggest that the greater ability of one permutation over the other to bind two HSF trimers accounts for the initial identification of the naturall occurring heat shock consensus sequence as a region of dyad symmetry.The eukaryotic heat shock transcription factor (HSF) is the main transcription factor responsible for expression of heat shock protein (hsp) genes during periods of stress. The activity of HSF is exquisitely sensitive to the presence of unfolded, denatured, or aberrant proteins, which appear to act as an intracellular signal to induce hsp gene transcription. It is likely that this signal acts on the posttranslational regulation of HSF activity, at least in part, through one of the heat shock proteins, hsp7O (reviewed in reference 16). Association of hsp70 with HSF appears to be necessary to sequester HSF in a form that is unable to activate transcription effectively. Any stress-induced increase in the concentration of aberrant proteins is thought to result in the titration of hsp70 and the accumulation of HSF in an active form.In vertebrate and Drosophila cells, the inactive form of HSF is a non-DNA-binding monomer (5,20,29). Heat shock causes the assembly of HSF monomers into trimers, which are then competent to bind DNA (5,20,29). In the yeast Saccharomyces cerevisiae, HSF is constitutively competent to bind DNA (11) and is trimeric even before heat shock (25).The observation that HSF is trimeric raises some interesting questions with regard to its DNA interaction. The initial analyses of natural heat shock elements (HSEs) resulted in the description of a consensus sequence, CTnGAAnnTTC nAG (17,18,27). This consensus HSE is palindromic, reminiscent of binding sites for dimeric proteins. It has more recently been suggested that functional HSEs are more properly described as inverted repeats of the sequence module nGAAn (2, 31). Within an array of nGAAn repeats, it is likely that each nGAAn element is contacted by a single HSF monomer; Perisic et al. (19) observed that repeats of two to three nGAAn elements are bound by a single trimer of Drosophila HSF, repeats of four to six elements are bound by two tri...
The heat shock transcription factor (HSF) of the yeast Saccharomyces cerevisiae is posttranslationally modified. At low growth temperatures, it activates transcription of heat shock genes only poorly; after shift to high temperatures, it activates transcription readily. In an effort to elucidate the mechanism of this regulation, we constructed a series of HSF-VP16 fusions that join the HSF DNA-binding domain to the strong transcriptional activation domain from the VP16 gene of herpes simplex virus. Replacement of the endogenous C-terminal transcriptional activation domain with that of VP16 generates an HSF derivative that exhibits behavior reminiscent of HSF itself: low transcriptional activation activity at normal growth temperature and high activity after heat shock. HSF can thus restrain the activity of the heterologous VP16 transcriptional activation domain. To determine what is required for repression of activity at low temperature, we deleted portions of HSF from this HSF-VP16 fusion to map the regulatory domain. We also isolated point mutations that convert the HSF-VP16 fusion into a constitutive transcriptional activator. We conclude that the central, evolutionarily conserved domain of HSF, encompassing the DNA-binding and multimerization domains, contains a major determinant of temperature-dependent regulation.Stress proteins, or heat shock proteins, are highly regulated, exhibiting low-level expression at low growth temperatures, intermediate levels at intermediate temperatures, and high levels at high temperatures. For Escherichia coli and the yeast Saccharomyces cerevisiae, the response to a temperature upshift is similar: a rapid increase in expression well above the original basal level, followed by adaptation to a new basal level that is only fewfold above the original.In eukaryotes, the major regulatory protein involved in heat shock protein expression is the transcriptional activator heat shock transcription factor (HSF). Indeed, the addition of a synthetic oligonucleotide bearing the HSF-binding site (a heat shock element) suffices to bring a heterologous gene under the control of the heat shock system (19, 29; this report). Therefore, to understand the regulation of heat shock protein expression, it is necessary to know how the activity of HSF is modulated such that it stimulates different levels of transcription at different temperatures.In Drosophila (30,39) example, reference 6) or of transcription factor activity (18,26,33,36) by phosphorylation. In most of these cases, it is either known or speculated that the effect of phosphorylation is to stabilize a conformation of the protein that exhibits higher (or lower) activity. It is relatively easy to imagine that HSF, whether from humans, flies, or yeasts, undergoes a conformational change upon phosphorylation and that the new conformation exhibits higher activity in DNA binding, transcriptional activation, or both (17,38).Existing data suggest that yeast HSF almost certainly undergoes a conformational change upon temperature upshift. First,...
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