Small ubiquitin-related modifier ligase activity of Mms21 is required for maintenance of chromosome integrity during the unperturbed mitotic cell division cycle in Saccharomyces cerevisiae.

The SUMO ligase activity of Mms21/Nse2, a conserved member of the Smc5/6 complex, is required for resisting extrinsically induced genotoxic stress. We report that the Mms21 SUMO ligase activity is also required during the unchallenged mitotic cell cycle in Saccharomyces cerevisiae. SUMO ligase-defective cells were slow growing and spontaneously incurred DNA damage. These cells required caffeine-sensitive Mec1 kinase-dependent checkpoint signaling for survival even in the absence of extrinsically induced genotoxic stress. SUMO ligase-defective cells were sensitive to replication stress and displayed synthetic growth defects with DNA damage checkpoint-defective mutants such as mec1, rad9, and rad24. MMS21 SUMO ligase and mediator of replication checkpoint 1 gene (MRC1) were epistatic with respect to hydroxyurea-induced replication stress or methyl methanesulfonate-induced DNA damage sensitivity. Subjecting Mms21 SUMO ligase-deficient cells to transient replication stress resulted in enhancement of cell cycle progression defects such as mitotic delay and accumulation of hyperploid cells. Consistent with the spontaneous activation of the DNA damage checkpoint pathway observed in the Mms21-mediated sumoylation-deficient cells, enhanced frequency of chromosome breakage and loss was detected in these mutant cells. A mutation in the conserved cysteine 221 that is engaged in coordination of the zinc ion in Loop 2 of the Mms21 SPL-RING E3 ligase catalytic domain resulted in strong replication stress sensitivity and also conferred slow growth and Mec1 dependence to unchallenged mitotically dividing cells. Our findings establish Mms21-mediated sumoylation as a determinant of cell cycle progression and maintenance of chromosome integrity during the unperturbed mitotic cell division cycle in budding yeast.

Design and synthesis of a new organic receptor and evaluation of colorimetric anion sensing ability in organo-aqueous medium.

A new organic receptor has been designed and synthesized by the combination of aromatic dialdehyde with nitro-substituted aminophenol resulting in a Schiff base compound. The receptor exhibited a colorimetric response for F(-) and AcO(-) ion with a distinct color change from pale yellow to red and pink respectively in dry DMSO solvent and yellow to pale greenish yellow in DMSO:H2O (9:1, v/v). UV-Vis titration studies displayed a significant shift in absorption maxima in comparison with the free receptor. The shift could be attributed to the hydrogen bonding interactions between the active anions and the hydroxyl functionality aided by the electron withdrawing nitro substituent on the receptor. (1)H NMR titration and density functionality studies have been performed to understand the nature of interaction of receptor and anions. The lower detection limit of 1.12ppm was obtained in organic media for F(-) ion confirming the real time application of the receptor.

Saliva: A tool in assessing glucose levels in Diabetes Mellitus.

BACKGROUND: Diabetes mellitus is a metabolic disorder affecting people worldwide, which require constant monitoring of their glucose levels. Commonly employed procedures include collection of blood or urine samples causing discomfort to the patients. Hence the need for an alternative non invasive technique is required to monitor glucose levels. Saliva present in the oral cavity not only maintains the health of the oral cavity but plays a important role in diagnosis of cancers of the oral cavity, periodontal diseases, HIV, heart diseases etc. The aim of the present study was undertaken to correlate the glucose levels in saliva and blood of diabetic and healthy non diabetic individuals and to determine the efficacy of saliva as a diagnostic tool. MATERIALS & METHODS: A total of 30 individuals of which 20 patients were diabetic patients and on medication and 10 patients were healthy non diabetic individuals were included in the study. Blood and saliva were collected under resting conditions and were subjected to glucose estimation. RESULTS: Salivary and blood glucose concentrations were determined in non diabetic healthy individuals (n=10) and Type II Diabetes mellitus patients (n=20). Glycosylated haemoglobin A1c was also determined in both Type II diabetic patients and Control group and a significant correlation (r=0.73) and (r=0.46) was found between HbA1c and serum glucose concentrations in diabetic and control group respectively. A significant correlation (r=0.54) and (r=0.45) was found between fasting blood glucose and fasting salivary glucose for diabetic group and control group respectively. A positive correlation (r=0.39) and (r=0.38) was found between fasting salivary glucose and HbA1c for diabetic and control group respectively. CONCLUSION: These findings suggest that the saliva can be used in the assessment of the blood glucose concentration in diabetes mellitus patients. How to cite the article: Satish BN, Srikala P, Maharudrappa B, Awanti M, Kumar P, Hugar D. Saliva: A tool in assessing glucose levels in Diabetes Mellitus. J Int Oral Health 2014;6(2):114-7.

Limiting the extent of the RDN1 heterochromatin domain by a silencing barrier and Sir2 protein levels in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, transcriptional silencing occurs at the cryptic mating-type loci (HML and HMR), telomeres, and ribosomal DNA (rDNA; RDN1). Silencing in the rDNA is unusual in that polymerase II (Pol II) promoters within RDN1 are repressed by Sir2 but not Sir3 or Sir4. rDNA silencing unidirectionally spreads leftward, but the mechanism of limiting its spreading is unclear. We searched for silencing barriers flanking the left end of RDN1 by using an established assay for detecting barriers to HMR silencing. Unexpectedly, the unique sequence immediately adjacent to RDN1, which overlaps a prominent cohesin binding site (CARL2), did not have appreciable barrier activity. Instead, a fragment located 2.4 kb to the left, containing a tRNA(Gln) gene and the Ty1 long terminal repeat, had robust barrier activity. The barrier activity was dependent on Pol III transcription of tRNA(Gln), the cohesin protein Smc1, and the SAS1 and Gcn5 histone acetyltransferases. The location of the barrier correlates with the detectable limit of rDNA silencing when SIR2 is overexpressed, where it blocks the spreading of rDNA heterochromatin. We propose a model in which normal Sir2 activity results in termination of silencing near the physical rDNA boundary, while tRNA(Gln) blocks silencing from spreading too far when nucleolar Sir2 pools become elevated.