Immunoprecipitation of RNA-DNA hybrid interacting proteins in Trypanosoma brucei reveals conserved and novel activities, including in the control of surface antigen expression needed for immune evasion by antigenic variation.

RNA-DNA hybrids are epigenetic features of genomes that provide a diverse and growing range of activities. Understanding of these functions has been informed by characterising the proteins that interact with the hybrids, but all such analyses have so far focused on mammals, meaning it is unclear if a similar spectrum of RNA-DNA hybrid interactors is found in other eukaryotes. The African trypanosome is a single-cell eukaryotic parasite of the Discoba grouping and displays substantial divergence in several aspects of core biology from its mammalian host. Here, we show that DNA-RNA hybrid immunoprecipitation coupled with mass spectrometry recovers 602 putative interactors in T. brucei mammal- and insect-infective cells, some providing activities also found in mammals and some lineage-specific. We demonstrate that loss of three factors, two putative helicases and a RAD51 paralogue, alters T. brucei nuclear RNA-DNA hybrid and DNA damage levels. Moreover, loss of each factor affects the operation of the parasite immune survival mechanism of antigenic variation. Thus, our work reveals the broad range of activities contributed by RNA-DNA hybrids to T. brucei biology, including new functions in host immune evasion as well as activities likely fundamental to eukaryotic genome function.

Técnicas fotoelásticas aplicadas al estudio de prótesis sobre implantes / No disponible

Se estudia, mediante métodos fotoelásticos, si el tipo de implante utilizado para soportar una prótesis es un factor que influye en la obtención de una distribución de cargas que minimice las fuerzas soportadas por el mismo. Se utilizan implantes de tres marcas distintas (Steri-Oss, Endopóre y 31), colocados por pares en tres modelos fotoelásticos de características iguales y se coloca un mismo puente de metal-porcelana en cada uno de ellos. Sobre cada modelo, se aplican fuerzas verticales oclusales en al primer molar y oblicuas oclusales en el canino. Se observan los modelos a través de un haz de luz polarizada para obtener las distribuciones de cargas en los mismos. Los análisis cualitativos de cada uno de los patrones cromáticos generados revelan que, en todos los casos, se obtiene una distribución mínima de cargas para el tipo de implantes Steri-Oss. Cuando las fuerzas aplicadas son de poco valor, los modelos con implantes Endopore tienen un peor comportamiento frente al tipo 3I, pero tienden a equiparar su compqrtamiento cuando las fuerzas aplicadas crecen en magnitud, generando patrones de cargas muy similares. Con las limitaciones inherentes a este estudio, se observa que el tipo de implante utilizado en una misma situación protésica, no influye significativamente en la respuesta a las fuerzas aplicadas (AU)

Using photoelastic methods, we study whether or not the kind of implant employed to hold prostheses together is a factor that has an influence on the stress distribution that minimizes the strengths supported by the implant itself. We employ three different brands of implants (Steri-Oss, Endopore and 3D, placed in pairs inside three photoelastic models, all of them with similar characteristics, and we put the same metal ceramic bridge over each one. Each model is subjected to vertical occlusal strengths in the first molar and oblique occlusal strengths in the canine. Models are observed through polarized light to obtain the stress distribution on them. In all cases, qualitative analysis of the chromatic patterns show that the minumum distribution of stress is obtained with Steri-Oss brand implants. When strengths are poor in quality, models with Endopore implants perform worse than models with 3.1 implants, but they tend to perform similarly when strengths are greater in maghitude,creating very similar stress patterns, Despite inherent limitations of this study, we can observe that the kind of implant employed in a prosthetic situation, does not have a meaningful effect on the response to strengths applied (AU)