Project description:While transcriptional regulation of stem cell self-renewal and differentiation has been extensively studied, only a small number of studies have addressed the roles for post-translational modifications in these processes. A key mechanism of post-translational modification is ubiquitination by the ubiquitin-proteasome system (UPS). Using UPS-targeted RNAi screens, we identify novel regulators of pluripotency and differentiation. We focus on two of these proteins, the deubiquitinating enzyme, Psmd14, and the E3 ligase, Fbxw7, and characterize their importance in ES cell pluripotency and cellular reprogramming. Embryonic stem cells were reverse transfected with siRNA, 48 hrs post transfection cells were isloated for RNA extraction and hybridization on Affymetrix microarrays
Project description:While transcriptional regulation of stem cell self-renewal and differentiation has been extensively studied, only a small number of studies have addressed the roles for post-translational modifications in these processes. A key mechanism of post-translational modification is ubiquitination by the ubiquitin-proteasome system (UPS). Using UPS-targeted RNAi screens, we identify novel regulators of pluripotency and differentiation. We focus on two of these proteins, the deubiquitinating enzyme, Psmd14, and the E3 ligase, Fbxw7, and characterize their importance in ES cell pluripotency and cellular reprogramming. Embryonic stem cells were reverse transfected with siRNA, and differentiated for 48hrs in conditions with retinoic acid, 48 hrs post transfection cells were isloated for RNA extraction and hybridization on Affymetrix microarrays
Project description:While transcriptional regulation of stem cell self-renewal and differentiation has been extensively studied, only a small number of studies have addressed the roles for post-translational modifications in these processes. A key mechanism of post-translational modification is ubiquitination by the ubiquitin-proteasome system (UPS). Using UPS-targeted RNAi screens, we identify novel regulators of pluripotency and differentiation. We focus on two of these proteins, the deubiquitinating enzyme, Psmd14, and the E3 ligase, Fbxw7, and characterize their importance in ES cell pluripotency and cellular reprogramming.
Project description:While transcriptional regulation of stem cell self-renewal and differentiation has been extensively studied, only a small number of studies have addressed the roles for post-translational modifications in these processes. A key mechanism of post-translational modification is ubiquitination by the ubiquitin-proteasome system (UPS). Using UPS-targeted RNAi screens, we identify novel regulators of pluripotency and differentiation. We focus on two of these proteins, the deubiquitinating enzyme, Psmd14, and the E3 ligase, Fbxw7, and characterize their importance in ES cell pluripotency and cellular reprogramming.
Project description:We established an assay to localize DNA-associated proteins that are slated for degradation by the ubiquitin-proteasome system. The genome-wide map we describe here ties proteolysis to active enhancer elements and to transcription start sites of specific gene families. ChIP-sequencing of ubiquitin and transcription factors was performed in the presence or absence of proteasome inhibition.
Project description:The ubiquitin proteasome system plays an important role in the pathophysiology of Multiple Myeloma, highlighted by the unique success of proteasome inhibitors in this malignancy. Using topic-defined microarrays we have looked at expression of ubiquitin proteasome system genes in 2 multiple myeloma cell lines and normal bone marrow samples.
Project description:Proctor2007 - Age related decline of proteolysis, ubiquitin-proteome system
This
is a stochastic model of the ubiquitin-proteasome system for a
generic pool of native proteins (NatP), which have a half-life of
about 10 hours under normal conditions. It is assumed that these
proteins are only degraded after they have lost their native
structure due to a damage event. This is represented in the model
by the misfolding reaction which depends on the level of reactive
oxygen species (ROS) in the cell. Misfolded proteins (MisP) are
first bound by an E3 ubiquitin ligase. Ubiquitin (Ub) is
activated by E1 (ubiquitin-activating enzyme) and then passed to
E2 (ubiquitin-conjugating enzyme). The E2 enzyme then passes the
ubiquitin molecule to the E3/MisP complex with the net effect
that the misfolded protein is monoubiquitinated and both E2 and
E3 are released. Further ubiquitin molecules are added in a
step-wise manner. When the chain of ubiquitin molecules is of
length 4 or more, the polyubiquitinated misfolded protein may
bind to the proteasome. The model also includes de-ubiquitinating
enzymes (DUB) which cleave ubiquitin molecules from the chain in
a step-wise manner. They work on chains attached to misfolded
proteins both unbound and bound to the proteasomes. Misfolded
proteins bound to the proteasome may be degraded releasing
ubiquitin. Misfolded proteins including ubiquitinated proteins
may also aggregate. Aggregates (AggP) may be sequestered
(Seq_AggP) which takes them out of harm's way or they may bind to
the proteasome (AggP_Proteasome). Proteasomes bound by aggregates
are no longer available for protein degradation.
Figure
2 and Figure 3 has been simulated using Gillespie2.
This model is described in the article:
An in silico model of the
ubiquitin-proteasome system that incorporates normal
homeostasis and age-related decline.
Proctor CJ, Tsirigotis M, Gray
DA.
BMC Syst Biol 2007; 1: 17
Abstract:
BACKGROUND: The ubiquitin-proteasome system is responsible
for homeostatic degradation of intact protein substrates as
well as the elimination of damaged or misfolded proteins that
might otherwise aggregate. During ageing there is a decline in
proteasome activity and an increase in aggregated proteins.
Many neurodegenerative diseases are characterised by the
presence of distinctive ubiquitin-positive inclusion bodies in
affected regions of the brain. These inclusions consist of
insoluble, unfolded, ubiquitinated polypeptides that fail to be
targeted and degraded by the proteasome. We are using a systems
biology approach to try and determine the primary event in the
decline in proteolytic capacity with age and whether there is
in fact a vicious cycle of inhibition, with accumulating
aggregates further inhibiting proteolysis, prompting
accumulation of aggregates and so on. A stochastic model of the
ubiquitin-proteasome system has been developed using the
Systems Biology Mark-up Language (SBML). Simulations are
carried out on the BASIS (Biology of Ageing e-Science
Integration and Simulation) system and the model output is
compared to experimental data wherein levels of ubiquitin and
ubiquitinated substrates are monitored in cultured cells under
various conditions. The model can be used to predict the
effects of different experimental procedures such as inhibition
of the proteasome or shutting down the enzyme cascade
responsible for ubiquitin conjugation. RESULTS: The model
output shows good agreement with experimental data under a
number of different conditions. However, our model predicts
that monomeric ubiquitin pools are always depleted under
conditions of proteasome inhibition, whereas experimental data
show that monomeric pools were depleted in IMR-90 cells but not
in ts20 cells, suggesting that cell lines vary in their ability
to replenish ubiquitin pools and there is the need to
incorporate ubiquitin turnover into the model. Sensitivity
analysis of the model revealed which parameters have an
important effect on protein turnover and aggregation kinetics.
CONCLUSION: We have developed a model of the
ubiquitin-proteasome system using an iterative approach of
model building and validation against experimental data. Using
SBML to encode the model ensures that it can be easily modified
and extended as more data become available. Important aspects
to be included in subsequent models are details of ubiquitin
turnover, models of autophagy, the inclusion of a pool of
short-lived proteins and further details of the aggregation
process.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000105.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:We performed 5hmC/5mC DNA Immunoprecipitation followed high-throughput sequencing using the cell sample along the whole TSKM secondary reprogramming system. The TSKM 0D is the fibroblasts deried from TSKM-iPS mouse as the starting cells of the reprogramming.The intermediate cells is 3-days induced cells which are refered as TSKM 3D cells, and the final reprogrammed cells is the iPS cells with full pluripotency driven from this secondary system. We compared the profiling of 5-hydroxymethylcytosine and 5-methylcytosine modifications in these different cell lines. We found that: a widespread accompanying increase of 5hmC and 5mC at TSS and ES-active regulation regions followed by 5mC-5hmC pattern switch. Taking the advantage of the newly established TSKM secondary reprogramming system, the epigenetic remodeling and regulation mechanisms can be further investigated to advance our understanding of the epigenetic barriers and decipher the dynamic mechanism in somatic cell reprogramming. Examination of 5-hydroxymethylcytosine/5-methylcytosine modifications in a Tet1-mediated secondary reprogramming system