1 research outputs found
Estudio del rol del factor UBF en la expresi贸n de poblaciones de rDNA variantes durante la adaptaci贸n estacional de Cyprinus carpio.
Tesis (Doctor en Biociencias Moleculares)RESUMEN: La biog茅nesis ribosomal es uno de los procesos cruciales a nivel celular. En la
regulaci贸n de este proceso participan dos mecanismos principales: uno que involucra los
factores de transcripci贸n cl谩sicos de la RNA polimerasa I (RNA PolI), y un segundo que
consiste en el despliegue de mecanismos epigen茅ticos. Actualmente, existe conocimiento de
que ambas v铆as se encontrar铆an 铆ntimamente relacionadas.
En este contexto el pez Cyprinus carpio (carpa), presenta caracter铆sticas especiales en
cuanto a la regulaci贸n de la biog茅nesis ribosomal. Previamente, se ha reportado que durante el
ciclo estacional este organismo debe implementar un proceso de adaptaci贸n a nivel molecular
para adecuar el proceso fundamental de s铆ntesis de ribosomas. La carpa durante la estaci贸n
invernal sufre una segregaci贸n de sus componentes nucleolares, acompa帽ada de un
reordenamiento de la cromatina nucleolar, lo cual finalmente se traduce en una disminuci贸n de
la expresi贸n de los genes ribosomales. Este fenotipo celular es revertido al llegar la estaci贸n
veraniega, continuando un proceso c铆clico gen茅ticamente programado denominado
aclimatizaci贸n estacional. Estos antecedentes han permitido postular que este organismo es
capaz de generar mecanismos moleculares de adaptaci贸n compensatorios frente a los cambios
en su entorno. Hasta nuestro conocimiento, la carpa constituye el 煤nico organismo en donde se
ha descrito y estudiado que el efecto de est铆mulos medioambientales es capaz de controlar la
transcripci贸n de los genes ribosomales a lo largo del ciclo estacional. Por esta raz贸n, C. carpio
es un extraordinario modelo de estudio tanto para el control de la biog茅nesis ribosomal, como
para profundizar el conocimiento sobre el efecto los est铆mulos medioambientales en la
reprogramaci贸n g茅nica de un organismo.
En este trabajo de tesis hemos centrado nuestro estudio en la prote铆na UBF (Upstream
Binding Factor). Esta prote铆na ha sido caracterizada como un factor de transcripci贸n de la
RNA PolI, que interviene en la formaci贸n del complejo de pre-iniciaci贸n sobre el promotor de
los genes ribosomales. Sin embargo, recientemente se ha descrito que este factor tambi茅n
interviene ayudando a mantener la transcripci贸n ribosomal activa. As铆, otros estudios han
demostrado que la prote铆na UBF no s贸lo se une al promotor del cistr贸n ribosomal, sino que
tambi茅n interact煤a con gran parte de la secuencia del cistron ribosomal. En este caso, UBF
desempe帽ar铆a un rol fundamental en la expresi贸n de las diferentes poblaciones de estos genes,..ABSTRACT: Ribosomal biogenesis is a critical process at a cellular level. Two main mechanisms
participate in the regulation of this process: one involving typical transcription factors of RNA
polymerase I (RNA Pol I) and a second consisting of a display of epigenetic mechanisms.
Nowadays, studies have proved that both pathways are closely related.
Cyprinus carpio (carp) has special features concerning ribosomal biogenesis
regulation. It has been previously reported that during each seasonal cycle, this organism must
go through an adaptation process at a molecular level in order to adjust the fundamental
process of ribosomal synthesis. During winter time, the carp undergoes a segregation process
of the nucleolar components along with a rearrangement of the nucleolar chromatin, which
results in a decreased expression of ribosomal genes. This cellular phenotype is reverted in the
summer season, thus creating a genetically programmed cyclical process known as seasonal
acclimatization. This suggests that this organism could generate compensatory molecular
adaptation mechanisms when its environment changes. To our knowledge, modulation of
ribosomal genes at a transcriptional level in response to environmental changes has been
described only in carp. For these reasons, C. carpio represents an excellent model to study the
mechanisms controlling ribosomal biogenesis, allowing us at the same time to deepen our
knowledge about the effects of environmental stimuli over this and other processes.
This thesis is focused on the protein UBF (Upstream Binding Factor), one of the
several factors involved in ribosomal regulation. This protein has been characterized as a
transcription factor for RNA Pol I, directly intervening in the formation of the pre-initiation
complex in the ribosomal gene. However, it has been recently reported that this factor also
acts as a maintainer of ribosomal transcription. Other studies have shown that UBF not only
binds to the promoter of the ribosomal cistron but also interacts with a large part of the
ribosomal gene sequence. If that is the case, UBF might have a significant role in the
expression of ribosomal genes, keeping them in a structurally active state. Overall, these allow
us to suggest UBF as a central factor in the regulation of ribosomal gene transcription, and our
hypothesis is that UBF differentially controls the expression of rRNA during seasonal
acclimation on C. Carpio by controlling the activity of a variant forms of rDNA (v-rDNA)..