MutSbeta exceeds MutSalpha in dinucleotide loop repair.

BACKGROUND: The target substrates of DNA mismatch recognising factors MutSalpha (MSH2+MSH6) and MutSbeta (MSH2+MSH3) have already been widely researched. However, the extent of their functional redundancy and clinical substance remains unclear. Mismatch repair (MMR)-deficient tumours are strongly associated with microsatellite instability (MSI) and the degree and type of MSI seem to be dependent on the MMR gene affected, and is linked to its substrate specificities. Deficiency in MSH2 and MSH6 is associated with both mononucleotide and dinucleotide repeat instability. Although no pathogenic MSH3 mutations have been reported, its deficiency is also suggested to cause low dinucleotide repeat instability. METHODS: To assess the substrate specificities and functionality of MutSalpha and MutSbeta we performed an in vitro MMR assay using three substrate constructs, GT mismatch, 1 and 2 nucleotide insertion/deletion loops (IDLs) in three different cell lines. RESULTS: Our results show that though MutSalpha alone seems to be responsible for GT and IDL1 repair, MutSalpha and MutSbeta indeed have functional redundancy in IDL2 repair and in contrast with earlier studies, MutSbeta seems to exceed MutSalpha. CONCLUSION: The finding is clinically relevant because the strong role of MutSbeta in IDL2 repair indicates MSH3 deficiency in tumours with low dinucleotide and no mononucleotide repeat instability.

Polymer translocation in a double-force arrangement.

Using Langevin dynamics simulations, we investigate the translocation dynamics of an externally driven polymer chain through a nanopore, where a pulling force F is exerted on the first monomer whilst there is an opposing force F(E) < F within the pore. Such a double-force arrangement has been proposed recently to allow better dynamical control of the translocation process in order to sequence biopolymers. We find that in the double-force arrangement translocation becomes slower as compared to the case under a single monomer pulling force of magnitude F-F(E), but scaling of the translocation time as a function of the chain length tau approximately N2 does not change. The waiting time tau(m) for monomer m to exit the pore is found to be a monotonically increasing function of the bead number almost until m approximately N , which indicates relatively well-defined slowing down and control of the chain velocity during translocation. We also study the waiting time distributions for the beads in the chain, and characterize in detail fluctuations in the bead positions and their transverse position coordinates during translocation. These data should be useful in estimating position-dependent sequencing errors in double-force experiments.

Germline MLH1 and MSH2 mutations in Italian pancreatic cancer patients with suspected Lynch syndrome.

Lynch syndrome is an inherited cancer syndrome caused by germline mutations in mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. LS predisposes to high risk of early-onset colorectal, endometrial and other tumors. Patients with Lynch syndrome have also been shown to have an elevated risk for pancreatic cancer (PC). In this study, we aimed to estimate the frequency of suspected Lynch syndrome among a series of 135 PC patients. Further, we wanted to determine the frequency of MMR gene mutations in the suspected Lynch syndrome cases. We also aimed to verify the pathogenicity of any novel non-truncating variants we might detect with a functional assay. Based on personal and/or familial cancer history, 19 patients were classified as suspected Lynch syndrome cases. DNA material for mutation analysis was available for eleven of them. Four patients were found to carry a total of five MLH1 or MSH2 variants. Of these, MSH2-Q402X, MSH2-G322D, and MLH1-K618A had been previously reported, while the MSH2-E205Q and MSH2-V367I variants were novel. MSH2-Q402X is a known stop mutation and reported here for the first time here in association with PC. MLH1-K618A was found in the unaffected branch of a kindred, suggesting that it may be a polymorphism or a low penetrance variant. MSH2-G322D likely does not cause a MMR defect, although this variant has also been associated with breast cancer as indeed seen in our patient. The novel variants MSH2-E205Q and MSH2-V367I were found in the same patient. Both novel variants were however functional in the applied MMR assay. Our findings suggest that only a small subset of pancreatic cancer patients carry pathogenic MMR mutations.

Quality of life during rehabilitation after coronary artery bypass surgery.

The effect of a three-phase comprehensive rehabilitation programme on the quality of life during the first postoperative year after coronary artery bypass surgery was studied in 205 male patients randomly allocated into a rehabilitation (R) and a hospital-based treatment (H) group. The rehabilitation programme included physical exercise, relaxation training, psychological group sessions, dietary advice and discussions about postoperative treatment of coronary disease. There was no difference between R and H groups in the frequency of postoperative complaints, number of hospital admissions and satisfaction of sexual life. An almost significantly greater number of subjects in R group than in H group perceived their health as good 12 months after surgery. The Beck Depression Index score decreased significantly in R group but not in H group during follow-up. A greater increase in hobby activities was observed in R group than in H group. More subjects in R group than in H group considered rehabilitation important for recovery, whereas more patients in H group considered support by the spouse and family, the subjective mental strength and a secure income as important.