The Rad1 gene is evolutionarily conserved from yeast to human. The fission yeast Schizosaccharomyces pombe Rad1 ortholog promotes cell survival against DNA damage and is required for G(2)/M checkpoint activation. In this study, mouse embryonic stem (ES) cells with a targeted deletion of Mrad1, the mouse ortholog of this gene, were created to evaluate its function in mammalian cells. Mrad1 (-/-) ES cells were highly sensitive to ultraviolet-light (UV light), hydroxyurea (HU) and gamma rays, and were defective in G(2)/M as well as S/M checkpoints. These data indicate that Mrad1 is required for repairing DNA lesions induced by UV-light, HU and gamma rays, and for mediating G(2)/M and S/M checkpoint controls. We further demonstrated that Mrad1 plays an important role in homologous recombination repair (HRR) in ES cells, but a minor HRR role in differentiated mouse cells.
Animals ; Cell Division ; Cell Proliferation ; DNA Damage ; DNA Repair ; Embryonic Stem Cells ; metabolism ; Exonucleases ; genetics ; metabolism ; physiology ; G2 Phase ; Gamma Rays ; Gene Deletion ; Hydroxyurea ; pharmacology ; Mice ; Ultraviolet Rays

Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and different charge isomers(CIs)is of utmost importance,but is challenging.We intended to quanti-tatively characterize the posttranslational modification status of CIs of antibody drugs and explore the impact of posttranslational modifications on charge heterogeneity.The CIs of antibodies were fraction-ated by strong cation exchange chromatography and verified by capillary isoelectric focusing-whole column imaging detection,followed by stepwise structural characterization at three levels.First,the differences between CIs were explored at the intact protein level using a top-down mass spectrometry approach;this showed differences in glycoforms and deamidation status.Second,at the peptide level,common modifications of oxidation,deamidation,and glycosylation were identified.Peptide mapping showed nonuniform deamidation and glycoform distribution among CIs.In total,10 N-glycoforms were detected by peptide mapping.Finally,an in-depth analysis of glycan variants of CIs was performed through the detection of enriched glycopeptides.Qualitative and quantitative analyses demonstrated the dynamics of 24 N-glycoforms.The results revealed that sialic acid modification is a critical factor ac-counting for charge heterogeneity,which is otherwise missed in peptide mapping and intact molecular weight analyses.This study demonstrated the importance of the comprehensive analyses of antibody CIs and provides a reference method for the quality control of biopharmaceutical analysis.

Objective The aim of this study was to investigate the effects of Rad9 mutants with impaired DNA mismatch repair ( MMR) function on the tumorigenesis of colorectal cancer. Methods The colorectal cancer tumor samples were collected from 100 patients. The mutation profiles of human Rad9 ( hRad9) gene in these samples were detected by reverse transcriptase?polymerase chain reaction ( RT?PCR) and sequencing. The plasmid of pFLAG?hRad9 ( L101M ) was constructed following the QuickChange mutagenesis procedure and transfected into mRad9?deleted mouse cells ( mRad9-/- cells) . The expression of hRad9 protein was measured by western blot analysis. The MMR activity in live cells was detected by flow cytometry using the reporter plasmid for MMR function. Results Mutation from Leu to Met at the residue 101 ( L101M) of hRad9 gene was detected in 7 of the 100 samples. The mismatch repair efficiency of mRad9-/-+L101M cells ( mRad9?deleted mouse cells with ectopic expression of L101M hRad9 gene) was (34.0± 5. 6)%, which was significantly lower than that in the mRad9-/-+ hRad9 cells [ mRad9?deleted mouse cells with ectopic expression of hRad9 gene, (48.0±7.5)%, P<0.05]. After N?nitroso?N?methylurea (MNU) treatment, the survival rate of mRad9-/-+L101M cells was (33.7±5.9)%, which was significantly higher than that in the mRad9-/-+ hRad9 cells [(21.3±4.7)%, P<0.05]. Thus, ectopic expression of L101M hRad9 gene resulted in significantly reduced MMR activity and increased resistance to MNU. Furthermore, ectopic expression of hRad9 gene with mutation at the target residues of post?translational modification in mRad9-/- cells also led to a reduced MMR activity. Conclusion Rad9 mutants with impaired DNA mismatch repair function may promote tumorigenesis of colorectal cancer.

Objective The aim of this study was to investigate the effects of Rad9 mutants with impaired DNA mismatch repair ( MMR) function on the tumorigenesis of colorectal cancer. Methods The colorectal cancer tumor samples were collected from 100 patients. The mutation profiles of human Rad9 ( hRad9) gene in these samples were detected by reverse transcriptase?polymerase chain reaction ( RT?PCR) and sequencing. The plasmid of pFLAG?hRad9 ( L101M ) was constructed following the QuickChange mutagenesis procedure and transfected into mRad9?deleted mouse cells ( mRad9-/- cells) . The expression of hRad9 protein was measured by western blot analysis. The MMR activity in live cells was detected by flow cytometry using the reporter plasmid for MMR function. Results Mutation from Leu to Met at the residue 101 ( L101M) of hRad9 gene was detected in 7 of the 100 samples. The mismatch repair efficiency of mRad9-/-+L101M cells ( mRad9?deleted mouse cells with ectopic expression of L101M hRad9 gene) was (34.0± 5. 6)%, which was significantly lower than that in the mRad9-/-+ hRad9 cells [ mRad9?deleted mouse cells with ectopic expression of hRad9 gene, (48.0±7.5)%, P<0.05]. After N?nitroso?N?methylurea (MNU) treatment, the survival rate of mRad9-/-+L101M cells was (33.7±5.9)%, which was significantly higher than that in the mRad9-/-+ hRad9 cells [(21.3±4.7)%, P<0.05]. Thus, ectopic expression of L101M hRad9 gene resulted in significantly reduced MMR activity and increased resistance to MNU. Furthermore, ectopic expression of hRad9 gene with mutation at the target residues of post?translational modification in mRad9-/- cells also led to a reduced MMR activity. Conclusion Rad9 mutants with impaired DNA mismatch repair function may promote tumorigenesis of colorectal cancer.