Specificity in the regulation of eukaryotic gene transcription

The regulation of eukaryotic gene transcription poses major challenges in terms of the innumerable protein factors required to ensure tissue or cell-type specificity. While this specificity is sought to be explained by the interaction of cis-acting DNA elements and the trans-acting protein factor(s), considerable amount of degeneracy has been observed in this interaction. Immunoglobulin heavy chain gene expression in A cells and liver-specific gene expression are discussed as examples of this complexity in this article. Heterodimerization and post-translational modification of transcription factors and the organization of composite promoter elements are strategies by which diverse sets of genes can be regulated in a specific manner using a finite number of protein factors

Studies on the synthesis of cytochrome P-450 and cytochrome P-448 in rat liver

The synthesis of cytochrome P-450 (phenobarbital inducible) and cytochrome P-448 (3-methylcholanthrene inducible) have been studied in rat liver in vivo and in the wheat germ cell-free system using anti-cytochrome P-450 and anti-cytochrome P-448 antibodies. The major mature forms synthesized in vivo correspond to a molecular weight of 47,000 for cytochrome P-450 and 53,000 for cytochrome P-448. Translation of poly(A)-containing RNA from phenobarbital-treated rats in the wheat germ cell-free system reveals that the cell-free product immunoprecipitated with anti-cytochrome P-450 antibody has a molecular weight close to 47,000. In the case of 3-methylcholanthrene, the cell-free product immunoprecipitated with anti-cytochrome P-448 antibody shows a molecular weight around 59,000. Significant conversion of the 59,000 species to the 53,000 species can be demonstrated when the translation is carried out in the presence of microsomal membranes isolated from rat liver. Phenobarbital and 3-methylcholanthrene enhance the translatable messenger RNA contents for cytochrome P-450 and cytochrome P-448, respectively

Segmented conjugated polymers

Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying excitation energies. The latter feature, especially when the chromophores are fluorescent, like in MEHPPV, makes these systems particularly interesting from the photophysics point of view. SegmentedMEHPPV-x samples, where x represents the mole fraction of conjugated segments, were prepared by a novel approach that utilizes a suitable precursor wherein selective elimination of one of the two eliminatable groups is affected; the uneliminated units serve as conjugation truncations. Control of the composition x of the precursor therefore permits one to prepare segmented MEHPPV-x samples with varying levels of conjugation (elimination). Using fluorescence spectroscopy, we have seen that even in single isolated polymer chains, energy migration from the shorter (higher energy) chromophores to longer (lower energy) ones occurs - the extent of which depends on the level of conjugation. Further, by varying the solvent composition, it is seen that the extent of energy transfer and the formation of poorly emissive inter-chromophore excitons are greatly enhanced with increasing amounts of non-solvent. A typical S-shaped curve represents the variation of emission yields as a function of composition suggestive of a cooperative collapse of the polymer coil, reminiscent of conformational transitions seen in biological macromolecules

Factors regulating the transcription of eukaryotic protein coding genes and their mechanism of action- a review

Protein factors play a crucial role in establishing gene-specific and cell-specific regulation of the process of transcription. These include general transcription factors which recognize TATA and CCAAT boxes and which form components of the RNA polymerase II system. Specific transcription factors interact with characteristic promoter elements of individual genes. Some of the examples are SP1, glucocorticoid receptor, GCN4, GAL4 and many others. Transcription factors have a DNA binding domain demarcated from the transcription activation domain. Some factors may have an additional ligand (small molecule) binding domain. Typical structural features such as helix-turn-helix motif, zinc finger and leucine zipper have been recognized in the DNA binding domain of the transcription factors. The acidic domain of the protein factors is involved in the transcription activation process. It appears that activation is the result of the combined action of several regulatory proteins binding at different regions of the promoter. Interaction between proteins bound to DNA but seperated by long stretches of nucleotides is facilitated by DNA bending. Functional specificity as well as diversity are feasible with a limited number of transcription factors through alterations in the architecture of interaction between a group of proteins bound to promoter elements

Regulation of Heme Biosynthesis in Neurospora crassa

The mold Neurospora crassa does not accumulate porphyrins in iron deficiency but instead accumulates the sideramine desferricoprogen. In iron deficiency there is an accumulation of δ-aminolevulinic acid and the δ-aminolevulinic acid dehydratase level is very low. A similar situation exists in cobalt toxicity and zinc deficiency. The δ-aminolevulinic acid synthetase and ferroprotoporphyrin chelatase comparatively show only marginal changes under these conditions. Addition of iron and zinc to the respective metal-deficient cultures results in an induction of δ-aminolevulinic acid dehydratase. The induction of δ-aminolevulinic acid dehydratase is repressed by protoporphyrin and less effectively by hemin and hemoglobin. Iron deficiency, zinc deficiency, and cobalt toxicity have been found to interfere with the conversion of protoporphyrin into heme, thus rendering protoporphyrin available to repress the enzyme. This repression can be counteracted by iron and much more effectively by coprogen. A model has been proposed in which protoporphyrin has been visualized as the corepressor for the enzyme δ-aminolevulinic acid dehydratase. It is held that iron in the form of coprogen converts protoporphyrin to heme, the latter having a lesser affinity for the aporepressor. Coprogen can inhibit heme binding to the aporepressor and thus render the repressor nonfunctional. This will lead to a derepression of the enzyme δ-aminolevulinic acid dehydratase

Science education in India - time to leapfrog with caution

There is a dire need to expand the scope for higher science education and research in the country to reach its goal of a knowledge power in the globe. Government agencies are announcing a massive increase in the number of such institutions on a daily basis. It is not, however, clear as to how we will get the adequate qualified human resource to man and run these new institutions bearing brand names of repute or fill in the existing vacancies. This article attempts to review the current situation and strategies planned. The bottom line is to provide an attractive career in terms of monetary benefits as well as working environment. In the meanwhile, should we not hasten carefully, if not slowly

Drugs and drug targets against malaria

The development of resistance by the parasite against first line and second line antimalarial drugs, has underscored the importance to develop new drug targets and pharmacophores to treat the disease. The absence of a vaccine for protection and the availability of artemisinin and its derivatives as the only option has made the situation rather serious. With the availability of increased support for malaria research, a variety of drug targets and candidate molecules are now available for further development. However, the success rate of a candidate molecule to become a drug is very low and it does become necessary to start with a large basket, identified on a rational basis. This review focuses on the present efforts to identify a variety of drug targets in the malaria parasite and to develop candidate drug molecules

La Vida e historia del rey Apolonio [¿Zaragoza, Juan Hurus, 1488?] y su trayectoria genérica*

En el artículo se analiza la diversa trayectoria genérica de la Vida e historia del rey Apolonio [¿Zaragoza, Juan Hurus, 1488?] desde una triple perspectiva. Por su origen, remonta a la Historia Apollonii regis Tyri, narración de origen clásico próxima a las novelas griegas. Su recepción hispánica se aleja de su género de creación, pues el texto es traducción de un capítulo de las Gesta romanorum, y se presentaría, impreso junto a los Siete sabios de Roma, como una historia ejemplar. Por último, la crítica moderna ha optado por insertarlo en la serie de los «romances de materia clásica» y en el género editorial de las «historias caballerescas breves»

SCREENING AND CHARACTERIZATION OF DEVELOPING RESISTANT CULTIVAR AGAINST ODOIPORUS LONGICOLLIS (OLIVIER) (COLEOPTERA: CURCULIONIDAE) USING REFERENCE GENOTYPES IN INDIA

Objective: The objective of the research was to develop a screening method for weevil resistance by using selected genotypes. The selected reference genotypes were screened against stem weevil to deals with the different parts in India.Methods: The collected stem pieces of each cultivar were cut into 30 cm length and kept in an insect breeding chamber for two polypropylene cages is one into another. The bottom of the inner cage is made holes to drain the water from stem discs and the outer cage is without holes to collect it. Reproductively active and healthy weevils (4 females and 4 males) were selected and released into the breeding chamber for each commercial cultivar and screened against Odoiporus longicollis and observation was taken after 38 d. Based on the following method, different states of insect cultures were screened under in vitro conditions. This experiment was replicated four times for further statistical analysis.Results: The resistant genotype had significantly more (p<0.05) mortality, and fewer than the susceptible genotypes. These results indicated that the genotypes can be used as reference genotypes in evaluating resistance or susceptibility against the banana stem weevil using Gas chromatography with antennogram detector. This implies that the infestation caused by the weevils varied in different genotypes and also this information will be further helpful in selecting the resistant cultivars for future in the field of Agriculture.Conclusion: In commercial cultivars, no one can report the divergent and screening of stem weevil under in vitro conditions. In field conditions, that are not accuracy because, Climate change, Adaptation of host, migration and etc. For this instance, we performed the in vitro screening study and it finally revealed the susceptible and resistant genotypes based on the percent of weevil infestation are the same as well as no significant differences between different banana growing areas in India.Keywords: Banana stem weevil (Odoiporus longicollis), Screening, Host-plant resistance, Resistant genotypes, Biodiversity, Gas chromatography with Electroantennogram detector (GC-EAD