Epigenetic regulation of Cyprinus carpio ribosomal criston during the acclimatization process
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Fecha
2012
Profesor/a Guía
Facultad/escuela
Idioma
en
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
Ribosomal RNA synthesis is the major transcriptional activity in a cell,
required for ribosome biogenesis, and it is critica! to ensure the supply of ribosomal
RNA in order to meet the cellular needs for protein synthesis. Considerable
evidence indicates that epigenetics is an important regulatory mechanism for this
intricate process. In addition, cells must also have the ability to maintain their
functions by constantly sensing and adapting to environmental variations
(homeostasis ).
Seasonal acclimatization of the fish Cyprinus carpía (common carp) requires
the implementation of complex molecular and cellular mechanisms to coordinate
"phenotypic plasticity." This process involves a reprogramming of gene expression,
which in turn integrates the homeostatic response. Our laboratory has reported that
in different cell types of the carp, the nucleolus undergoes a dramatic
rearrangement of its molecular structure. During winter, fibrillar and granular
components of the nucleolus are segregated and surrounded by a thick layer of
heterochromatin, which is an ultrastructural feature accompanied by a transient
repression of ribosomal RNA transcription. In contrast, this condition is reversed
during the summer, and is associated with a recovery of active ribosomal
biosynthesis. Thus, the process of seasonal adaptation in the carp certainly
involves a fine modulation of the transcriptional activity of ribosomal genes (rDNA).
Recent studies on the regulation of ribosomal genes indicate that the
numerous copies of rDNA are comprised of at least two distinct transcriptional states: active or silenced. The two states can be differentiated by their chromatin
configuration and may require specific triggers to be interconverted. Thus, the use
of epigenetic mechanisms to control chromatin architecture may represent an
important strategy to modulate and switch the transcriptional activity of rDNA
during seasonal adaptation
In this context, the protein TTF-1 has been described as playing a central
role in the transcriptional modulation of ribosomal genes through its interaction with
epigenetic modifiers, such as the nucleolar remodeling complex (NoRC), thus
playing an active role in the silencing of rDNA transcription.
Most of the conclusions regarding regulatory mechanisms that control rRNA
transcription have been proposed based on in vítro approaches. Thus, the natural
cyclic modulation of rRNA transcriptional activity observed during carp
acclimatization emerges as a valuable model towards studying the overall
phenomenon in a living organism.
Therefore, the general purpose of this thesis consists in studying the
epigenetic regulation of the ribosomal cistron during the acclimatization process of
the Cyprínus carpía. Consequently, our hypothesis proposes that "The factor TTF-1
and the chromatin remodeling complex NoRC contribute significantly to the
negative regulation of transcriptional expression of rRNAs during the seasonal
adaptation of Cyprínus carpía."
Thus our results represent a first approach in epigenetic control involved in
the expression of ribosomal genes in a natural context, where the factor TTF-1 and
NoRC complex play a fundamental role during the carp acclimatization process.
Notas
Tesis (Doctor en Biociencias Moleculares)
Palabras clave
Pez Carpa, Climatización, Chile