Interferència mediada per RNA, una nova revolució genètica

Els RNA (o ARN, àcids ribonucleics) són biomolècules lineals de cadena senzilla, com un fil, formades per la unió seqüencial d'altres molècules més senzilles, els nucleòtids. Abans de la descoberta del fenòmen de RNAi es creia que el RNA era només un intermediari silenciós de la maquinària genètica, que transportava cegament les instruccions dels gens, en descodificava el missatge i el convertia en proteïnes, procés que es coneix amb el nom de flux d'informació genètica (del gen, que emmagatzema la informació i és format per ADN, a les proteïnes, que fan la feina especificada pel gen) [...].

Transgenic passionfruit expressing RNA derived from Cowpea aphid-borne mosaic virus is resistant to passionfruit woodiness disease

Sixteen transgenic yellow passionfruit (Passiflora spp.) plants (R0) were obtained which express a non-translatable transgenic RNA corresponding to the 3' region of the NIb gene and the 5' region of the CP gene, derived from the genome of a Brazilian isolate of Cowpea aphid-borne mosaic virus (CABMV). The transgenic plants were propagated by stem cuttings and challenged by sap inoculation with isolates CABMV-MG1 and CABMV-PE1. One transgenic plant (TE5-10) was resistant to the isolate CABMV-MG1, but susceptible to CABMV-PE1. The remaining transgenic plants developed systemic symptoms, equal to non-transformed plants, when inoculated with either isolate. The absence of virus in TE5-10 plants was confirmed by indirect ELISA. Transcription analysis of the transgene demonstrated that the TE5-10 plant did not accumulate transgenic mRNA, even before inoculation. After inoculation, viral RNA was only detected in plants inoculated with CABMV-PE1. These results confirm that the transgenic plant TE5-10 is resistant to isolate CABMV-MG1, and suggest that the resistance mechanism is post-transcriptional gene silencing, which is already activated in the transgenic plants before virus inoculation.

Viróides e virusóides: relíquias do mundo de RNA

Até meados do século XX, os vírus eram considerados os representantes mais simples da escala biológica. A descoberta dos RNAs satélites e dos viróides por volta de 1970 foi surpreendente, pois comprovou-se a existência de uma nova classe de moléculas auto-replicativas ainda mais simples, denominada agentes sub-virais. Há indícios de que os viróides e virusóides (que formam uma classe de RNAs satélites), teriam feito parte do "Mundo de RNA" (que precedeu o mundo atual baseado no DNA e proteínas), podendo ser considerados fósseis moleculares dessa era antiga. A simplicidade desses agentes sub-virais e o fato de que a molécula de RNA deve interagir diretamente com fatores do hospedeiro para o desenvolvimento do seu ciclo infeccioso colocam esses patógenos como um modelo para o estudo de processos metabólicos celulares. Nos últimos anos, tem-se observado um volume grande de publicações visando elucidar aspectos da interação viróide/hospedeiro, como os mecanismos da patogênese, movimento dos viróides nas plantas hospedeiras, silenciamento gênico e atividades das ribozimas. Mudanças recentes ocorridas na taxonomia desses patógenos com a criação de famílias, gêneros e espécies, além da descoberta de novos viróides, também têm sido verificadas. A presente revisão visa atualizar o leitor quanto aos recentes avanços nas pesquisas com viróides, principalmente na taxonomia, filogenia e em vários aspectos moleculares da interação viróide/hospedeiro. Estão incluídas também algumas características dos virusóides e sua relação evolutiva com os viróides.

The Significance of Hydrogen Bonding Interactions in the Cleavage of RNA

RNA is essential for all living organisms. It has important roles in protein synthesis, controlling gene expression as well as catalyzing biological reactions. Chemically RNA is a very stable molecule, although in biological systems many agents catalyze the cleavage of RNA, such as naturally occurring enzymes and ribozymes. Much effort has been put in the last decades in developing highly active artificial ribonucleases since such molecules could have potential in the therapeutic field and provide tools for molecular biology. Several potential catalysts have emerged, but usually detailed cleavage mechanism remains unresolved. This thesis is aimed at clarifying mechanistic details of the cleavage and isomerization of RNA by using simpler nucleoside models of RNA. The topics in the experimental part cover three different studies, one concerning the mechanism of catalysis by large ribozymes, one dealing with the reactivity of modified and unmodified RNA oligonucleotides and one showing an efficient catalysis of the cleavage and isomerization of an RNA phosphodiester bond by a dinuclear metal ion complex. A review of the literature concerning stabilization of the phosphorane intermediate of the hydrolysis and isomerization of RNA phosphodiester bond is first presented. The results obtained in the experimental work followed by mechanistic interpretations are introduced in the second part of the thesis. Especially the significance of hydrogen bonding interactions is discussed.

Unca Don and Unca Scrooge’s Guide to History. Representations of the Past in the Disney Comics of Don Rosa

This thesis studies the various forms and layers of representations of the past that can be found in the Disney comics of Don Rosa. To stay true to the legacy of renowned comic book artist Carl Barks, Rosa has stopped time in the duck universe to the 1950’s: the decade when Barks created his most noted stories. There is a special feel of historicalness in Rosa’s duck stories, as his characters recall events that occurred in both Rosa’s own stories as well as Barks’. Rosa has shed new light to the past of the characters by writing and illustrating the history of Scrooge McDuck, one of the most beloved Disney characters. Rosa is also adamant that the historical facts used in his stories are always correct and based on thorough research. The methodological tools used in the analysis of the comics come from the fields of comic book studies, film theory, and history culture. Film and comics are recognized by many scholars as very similar media, which share elements that make them comparable in many ways. This thesis utilizes studies on historical film, narrative and genre, which provide valuable insight and comparisons for analysis. The thesis consists of three main chapters, the first of which deconstructs the duck universe in the stories in order to understand how the historicalness in them is created,and which outside elements might affect them, including the genre of Disney comics, publishers, and the legacy of Barks. The next chapter focuses on The Life and Times of Scrooge McDuck series, i.e. the stories which are located in the past. Such stories feature similar representations of history as for example Westerns. They also compress and alter history to meet the restrictions of the medium of comics. The last part focuses on the adventure stories which draw inspiration from for example mythology, and take the characters to strange and mystical, but yet historical worlds. Such treasure-hunting stories show similarity to the action-adventure genre in film and for example their stereotypical representations of foreign cultures. Finally, the chapter addresses the problematic of historical fiction and its capability to write history.

The Helsinki tourist-guide

kuv., 14 x 19 cm

A guide to Helsingfors

kuv., 12 x 18 cm

1922 Guide for travellers to Helsingfors

kuv., 11 x 17 cm

Guide for travellers to Helsingfors

kuv., 11 x 17 cm

Guide to Helsingfors

kuv., 12 x 22 cm

Guide to Helsingfors

kuv., 12 x 22 cm

Tampere guide

kuv., 12 x 21 cm

Tampere guide

kuv., 12 x 21 cm