Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains...Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation(LLPS)when facing DNA double-strand breaks(DSBs).The histone methyltransferase SUVR2(MtSUVR2)has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation(H3K9me1)to H3K9me2/3 in vitro and in Medicago truncatula.Under DNA damage,the proportion of heterochromatin decreased and the level of DSB damage marker y-H2AX increased in suvr2 mutants,indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage.Interestingly,MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites,and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments.The IDR1 and lowcomplexity domain regions of MtSUVR2 determined its phase separation in the nucleus,whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51.Furthermore,we found that MtSUVR2 drove the phase separation of MtRAD51 to form"DNA repair bodies,"which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells.Taken together,our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.展开更多
The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remod...The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remodeling proteins CHR19,CHR27, and CHR28(CHR19/27/28), which are also involved in transcriptional gene silencing. Here our study demonstrated that SUVR2 is almost fully mono-sumoylated in vivo. We successfully identified the exact SUVR2 sumoylation site by combining in vitro mass spectrometric analysis and in vivo immunoblotting confirmation. The luminescence imaging assay and quantitative RT-PCR results demonstrated that SUVR2 sumoylation is involved in transcriptional gene silencing. Furthermore, we found that SUVR2 sumoylation is required for the interaction of SUVR2 with CHR19/27/28, which is consistent with the fact that SUMO proteins are necessary for transcriptional gene silencing. These results suggest that SUVR2 sumoylation contributes to transcriptional gene silencing by facilitating the interaction of SUVR2 with the chromatin-remodeling proteins CHR19/27/28.展开更多
Local cerebral metabolic rate of glucose(LCMRGlc) is an important index for the description of neural function.Dynamic 18 F-fluoro-2-deoxy-D-glucose(FDG) positron emission tomography(PET) has been used for quantitativ...Local cerebral metabolic rate of glucose(LCMRGlc) is an important index for the description of neural function.Dynamic 18 F-fluoro-2-deoxy-D-glucose(FDG) positron emission tomography(PET) has been used for quantitative imaging of LCMRGlc in humans,but is seldom used routinely because of the difficulty in obtaining the input function noninvasively.A reference tissue-based Patlak plot model(rPatlak) was proposed to generate parametric images of LCMRGlc in a quantitative dynamic FDG-PET study without requiring blood sampling.Dynamic emission scans(4×0.5,4×2 and 10×5 min) were acquired simultaneously with an IV bolus injection of 155 MBq of FDG.Arterial blood samples were collected during the scans via a catheter placed in the radial artery.Simulation data were also generated using the same scan sequence.The last ten scan data sets were used in a graphical analysis using the Patlak plot.The ratio of LCMRGlc estimated from the original Patlak(oPatlak,using plasma input) was used as the gold standard,and the standardized uptake value ratio(SUVR) was also calculated for comparison.Eight different tissues including white matter,gray matter,and whole brain were chosen as reference tissues for evaluation.Regardless of the reference region used,the slopes in the linear regression between oPatlak and rPatlak were closer to unity than the regression slopes between oPatlak and SUVR.The intercepts for the former were also closer to 0 than those for the latter case.The squared correlation coefficients were close to 1.0 for both cases.This showed that the results of rPatlak were in good agreement with those of oPatlak,however,SUVR exhibited more deviation.The simulation study also showed that the relative variance and bias for rPatlak were less than those for SUVR.The images obtained with rPatlak were very similar to those obtained with oPatlak,while there were differences in the relative spatial distribution between the images of SUVR and oPatlak.This study validates that the rPatlak method is better than the SUVR method and is a good approximation to the oPatlak method.The new method is suitable for generating LCMRGlc parametric images noninvasively.展开更多
基金the Key Projects in Science and Technology of Inner Mongolia(2021ZD0031)the Opening Fund of the Key Laboratory of Forage and Endemic Crop Biology,the Ministry of Education(FECBOF2021001)+1 种基金the National Natural Science Foundation of China(NFSC32070272)for supporting this work.
文摘Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation(LLPS)when facing DNA double-strand breaks(DSBs).The histone methyltransferase SUVR2(MtSUVR2)has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation(H3K9me1)to H3K9me2/3 in vitro and in Medicago truncatula.Under DNA damage,the proportion of heterochromatin decreased and the level of DSB damage marker y-H2AX increased in suvr2 mutants,indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage.Interestingly,MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites,and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments.The IDR1 and lowcomplexity domain regions of MtSUVR2 determined its phase separation in the nucleus,whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51.Furthermore,we found that MtSUVR2 drove the phase separation of MtRAD51 to form"DNA repair bodies,"which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells.Taken together,our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.
基金supported by the National Key Research and Development Program of China (2016YFA0500801 to Xinjian He)
文摘The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remodeling proteins CHR19,CHR27, and CHR28(CHR19/27/28), which are also involved in transcriptional gene silencing. Here our study demonstrated that SUVR2 is almost fully mono-sumoylated in vivo. We successfully identified the exact SUVR2 sumoylation site by combining in vitro mass spectrometric analysis and in vivo immunoblotting confirmation. The luminescence imaging assay and quantitative RT-PCR results demonstrated that SUVR2 sumoylation is involved in transcriptional gene silencing. Furthermore, we found that SUVR2 sumoylation is required for the interaction of SUVR2 with CHR19/27/28, which is consistent with the fact that SUMO proteins are necessary for transcriptional gene silencing. These results suggest that SUVR2 sumoylation contributes to transcriptional gene silencing by facilitating the interaction of SUVR2 with the chromatin-remodeling proteins CHR19/27/28.
基金supported by the National Natural Science Foundation of China (30840033,30770615 and 30970818)the National Basic Research Program of China (2011CB707701)the Joint Research Foundation of Beijing Education Committee (JD100010607)
文摘Local cerebral metabolic rate of glucose(LCMRGlc) is an important index for the description of neural function.Dynamic 18 F-fluoro-2-deoxy-D-glucose(FDG) positron emission tomography(PET) has been used for quantitative imaging of LCMRGlc in humans,but is seldom used routinely because of the difficulty in obtaining the input function noninvasively.A reference tissue-based Patlak plot model(rPatlak) was proposed to generate parametric images of LCMRGlc in a quantitative dynamic FDG-PET study without requiring blood sampling.Dynamic emission scans(4×0.5,4×2 and 10×5 min) were acquired simultaneously with an IV bolus injection of 155 MBq of FDG.Arterial blood samples were collected during the scans via a catheter placed in the radial artery.Simulation data were also generated using the same scan sequence.The last ten scan data sets were used in a graphical analysis using the Patlak plot.The ratio of LCMRGlc estimated from the original Patlak(oPatlak,using plasma input) was used as the gold standard,and the standardized uptake value ratio(SUVR) was also calculated for comparison.Eight different tissues including white matter,gray matter,and whole brain were chosen as reference tissues for evaluation.Regardless of the reference region used,the slopes in the linear regression between oPatlak and rPatlak were closer to unity than the regression slopes between oPatlak and SUVR.The intercepts for the former were also closer to 0 than those for the latter case.The squared correlation coefficients were close to 1.0 for both cases.This showed that the results of rPatlak were in good agreement with those of oPatlak,however,SUVR exhibited more deviation.The simulation study also showed that the relative variance and bias for rPatlak were less than those for SUVR.The images obtained with rPatlak were very similar to those obtained with oPatlak,while there were differences in the relative spatial distribution between the images of SUVR and oPatlak.This study validates that the rPatlak method is better than the SUVR method and is a good approximation to the oPatlak method.The new method is suitable for generating LCMRGlc parametric images noninvasively.
