7 research outputs found
Transcriptional outcomes (fates) in response to DNA damage
Various types of DNA damage interfere with key vital processes which use DNA as a template, like replication and transcription. Upon large amount of genotoxic impacts, transcription is over-activated and probably results in the activation of several DNA damage recognition processes. During transcrip-tion, numerous components of the transcription machinery may act as a platform to recruit repair proteins at break sites. In contrast to that, when DNA damage occurs at a transcribing unit, it leads to transcriptional block. This multistep process in-volves several kinases and the ubiquitin ligases like NEDD4 and CUL3 leading to proteasome dependent degradation of RNA polymerase II (RNAPII) which happens at the site of the damage. Finally, at the break site ddRNA (a new class of noncoding RNA) production could be observed by controlling the DDR activation at sites of DNA damage. Taken together these results support an uncharacterized function of RNAPII complexes which allow the rec-ognition of DNA damages and like this enhance cell survival following DNA damage. This work was supported by OTKA-PD [112118], and the JĂĄnos Bolyai Research Scholarship of the Hungarian Acad-emy of Sciences
Mechanistic insights into the transcriptional arrest in the presence of Double Strand Breaks
Double-strand breaks (DSBs) occur frequently in
the genome during genome replication or by DNA
damaging agents. DNA lesions affect fundamental
DNA-dependent nuclear processes, such as
replication and transcription. We have developed
an experimental system where DSBs are induced
at coding regions of RNA polymerase II transcribing
genes. We have started to study the kinetics of RNA
polymerase II transcription inhibition in the presence
of DNA breaks. We observed that induction of the
break led to transcription inhibition and the restoration
of transcription closely followed the dynamics of
the repair of breaks. We confirmed by chromatinimmunoprecipitation
that the break induction led to
displacement of RNA polymerase II affecting both
the elongation and the initiation of transcription. Our
results show that this is dependent on one of the
major kinase in DNA damage repair called DNAPKcs.
We also investigated the downstream steps of RNA
polymerase II removal and we claimed that it was
a multistep process involving additional kinases and
ubiquitin ligases NEDD4 and CUL3. At the last step
of break dependent transcriptional silencing the RNA
polymerase II is targeted for proteasome dependent
degradation. These data demonstrate that the DNA
damage repair complexes and proteasomal system
have a synergistic and active role in transcriptional
silencing during the DSB repair by removing the RNA
pol II from the transcribing region. We show here
that DNA lesions occurring at transcribed regions
cause a transient repression until the lesion is
repaired. This is probably a cell defense mechanism
to avoid production of truncated or mutated
transcripts in essential genes whose alterations in
their gene expression would endanger cell viability.
Understudying the role of DNAPKcs, in preventing
RNA pol II bypassing a DSB might be a key in
avoiding the production of mutated transcripts that
could lead to cancerous phenotypes
WWP2 ubiquitylates RNA polymerase II for DNA-PK-dependent transcription arrest and repair at DNA breaks
DNA double-strand breaks (DSBs) at RNA polymerase II (RNAPII) transcribed genes lead to inhibition of transcription. The DNA-dependent protein kinase (DNA-PK) complex plays a pivotal role in transcription inhibition at DSBs by stimulating proteasome-dependent eviction of RNAPII at these lesions. How DNA-PK triggers RNAPII eviction to inhibit transcription at DSBs remains unclear. Here we show that the HECT E3 ubiquitin ligase WWP2 associates with components of the DNA-PK and RNAPII complexes and is recruited to DSBs at RNAPII transcribed genes. In response to DSBs, WWP2 targets the RNAPII subunit RPB1 for K48-linked ubiquitylation, thereby driving DNA-PK- and proteasome-dependent eviction of RNAPII. The lack of WWP2 or expression of nonubiquitylatable RPB1 abrogates the binding of nonhomologous end joining (NHEJ) factors, including DNA-PK and XRCC4/DNA ligase IV, and impairs DSB repair. These findings suggest that WWP2 operates in a DNA-PK-dependent shutoff circuitry for RNAPII clearance that promotes DSB repair by protecting the NHEJ machinery from collision with the transcription machinery
Asynchronous recovery of predators and prey conditions resilience to drought in a neotropical ecosystem
International audienceThe predicted increase in the intensity and frequency of drought events associated with global climate change will impose severe hydrological stress to freshwater ecosystems, potentially altering their structure and function. Unlike freshwater communities' direct response to drought, their post-drought recovery capacities remain understudied despite being an essential component driving ecosystem resilience. Here we used tank bromeliad as model ecosystem to emulate droughts of different duration and then assess the recovery capacities of ecosystem structure and function. We followed macroinvertebrate predator and prey biomass to characterize the recovery dynamics of trophic structure (i.e. predator-prey biomass ratio) during the post-drought rewetting phase. We showed that drought significantly affects the trophic structure of macroinvertebrates by reducing the predatorprey biomass ratio. The asynchronous recovery of predator and prey biomass appeared as a critical driver of the post-drought recovery trajectory of trophic structure. Litter decomposition rate, which is an essential ecosystem function, remained stable after drought events, indicating the presence of compensatory effects between detritivores biomass and detritivores feeding activity. We conclude that, in a context of global change, the asynchrony in post-drought recovery of different trophic levels may impact the overall drought resilience of small freshwater ecosystems in a more complex way than expected
In situ resistance, not immigration, supports invertebrate community resilience to drought intensification in a Neotropical ecosystem
International audienceWhile future climate scenarios predict declines in precipitations in many regions of the world, little is known of the mechanisms underlying community resilience to prolonged dry seasons, especially in ânaĂŻveâ Neotropical rainforests. Predictions of community resilience to intensifying drought are complicated by the fact that the underlying mechanisms are mediated by species' tolerance and resistance traits, as well as rescue through dispersal from source patches.We examined the contribution of in situ toleranceâresistance and immigration to community resilience, following drought events that ranged from the ambient norm to IPCC scenarios and extreme events. We used rainshelters above rainwaterâfilled bromeliads of French Guiana to emulate a gradient of drought intensity (from 1 to 3.6 times the current number of consecutive days without rainfall), and we analysed the postâdrought dynamics of the taxonomic and functional community structure of aquatic invertebrates to these treatments when immigration is excluded (by netting bromeliads) or permitted (no nets). Drought intensity negatively affected invertebrate community resistance, but had a positive influence on community recovery during the postâdrought phase. After droughts of 1 to 1.4 times the current intensities, the overall invertebrate abundance recovered within invertebrate life cycle durations (up to 2 months). Shifts in taxonomic composition were more important after longer droughts, but overall, community composition showed recovery towards baseline states. The nonârandom patterns of changes in functional community structure indicated that deterministic processes like environmental filtering of traits drive community reâassembly patterns after a drought event. Community resilience mostly relied on in situ toleranceâresistance traits. A rescue effect of immigration after a drought event was weak and mostly apparent under extreme droughts.Under climate change scenarios of drought intensification in Neotropical regions, community and ecosystem resilience could primarily depend on the persistence of suitable habitats and on the resistance traits of species, while metacommunity dynamics could make a minor contribution to ecosystem recovery. Climate change adaptation should thus aim at identifying and preserving local conditions that foster in situ resistance and the buffering effects of habitat features
A new approach of monitoring and physically-based modelling to investigate urban wash-off process on a road catchment near Paris
International audienceNowadays, the increasing use of vehicles is causing contaminated stormwater runoff to drain from roads. The detailed understanding of urban wash-off processes is essential for addressing urban management issues. However, existing modelling approaches are rarely applied for these objectives due to the lack of realistic input data, unsuitability of physical descriptions, and inadequate documentation of model testing. In this context, we implement a method of coupling monitoring surveys with the physically-based FullSWOF (Full Shallow Water equations for Overland Flow) model (Delestre et al., 2014) and the process-based H-R (Hairsine-Rose) model (Hairsine and Rose, 1992a, 1992b) to evaluate urban wash-off process on a road catchment near Paris (Le Perreux sur Marne, Val de Marne, France, 2661 m2). This work is the first time that such an approach is applied for road wash-off modelling in the context of urban stormwater runoff. On-site experimental measurements have shown that only the finest particles of the road dry stocks could be transferred to the sewer inlet during rainfall events, and most Polycyclic Aromatic Hydrocarbons (PAHs) are found in the particulate phase. Simulations over different rainfall events represent promising results in reproducing the various dynamics of water flows and sediment transports at the road catchment scale. Elementary Effects method is applied for sensitivity analysis. It is confirmed that settling velocity (Vs) and initial dry stocks (S) are the most influential parameters in both overall and higher order effects. Furthermore, flow-driven detachment seems to be insignificant in our case study, while raindrop-driven detachment is shown to be the major force for detaching sediment from the studied urban surface. Finally, a multiple sediment classification regarding the Particle Size Distribution (PSD) can be suggested for improving the model performance for future studies