Characterization of biochemical properties of Bacillus subtilis RecQ helicase.

RecQ family helicases function as safeguards of the genome. Unlike Escherichia coli, the Gram-positive Bacillus subtilis bacterium possesses two RecQ-like homologues, RecQ[Bs] and RecS, which are required for the repair of DNA double-strand breaks. RecQ[Bs] also binds to the forked DNA to ensure a smooth progression of the cell cycle. Here we present the first biochemical analysis of recombinant RecQ[Bs]. RecQ[Bs] binds weakly to single-stranded DNA (ssDNA) and blunt-ended double-stranded DNA (dsDNA) but strongly to forked dsDNA. The protein exhibits a DNA-stimulated ATPase activity and ATP- and Mg(2+)-dependent DNA helicase activity with a 3' → 5' polarity. Molecular modeling shows that RecQ[Bs] shares high sequence and structure similarity with E. coli RecQ. Surprisingly, RecQ[Bs] resembles the truncated Saccharomyces cerevisiae Sgs1 and human RecQ helicases more than RecQ[Ec] with regard to its enzymatic activities. Specifically, RecQ[Bs] unwinds forked dsDNA and DNA duplexes with a 3'-overhang but is inactive on blunt-ended dsDNA and 5'-overhung duplexes. Interestingly, RecQ[Bs] unwinds blunt-ended DNA with structural features, including nicks, gaps, 5'-flaps, Kappa joints, synthetic replication forks, and Holliday junctions. We discuss these findings in the context of RecQ[Bs]'s possible functions in preserving genomic stability.

Effect of cigarette smoking on clinical outcomes of hospitalized Chinese male smokers with acute myocardial infarction.

BACKGROUND: Smoking is known to be a strong risk factor for premature atherosclerosis, acute myocardial infarction (AMI) and sudden cardiac death. According to a cross-sectional survey conducted in 2000 - 2001 in China, the prevalence of smoking among the Chinese men was 60.2%, the highest prevalence in the world. Up to date, the relationship between smoking and AMI in Chinese male smokers is still unclear. This study analyzed the baseline characteristics for male smokers hospitalized with AMI and investigated the effect of cigarette smoking on their clinical outcomes. METHODS: A total of 890 men aged 18 years or over with AMI were prospectively recruited from 1 January 2007 to 31 December 2009 from Shanxi Provincial People's Hospital. Patients were grouped into smokers and nonsmokers. The relationships between baseline characteristics and clinical outcomes were tested using either the chi-square test for trend for discrete variables or analysis of variance for continuous variables. RESULTS: Smokers accounted for 66.7% (594), more than twice of nonsmokers (296 (33.3%)), and were averaged 7 years younger ((56.61 ± 11.44) vs. (63.61 ± 11.62) years, P < 0.001). Smokers had the higher rate of TIMI flow grade 2 or 3 after thrombolytic therapy (42.4% vs. 24.5%, P = 0.002), 1 vessel disease (25.5% vs. 14.5%, P = 0.003) than nonsmokers. Smokers had better in-hospital outcome with lower in-hospital mortality rate than nonsmokers (6.2% vs. 10.8%, P = 0.023). CONCLUSIONS: Male smokers suffered from AMI in this study presented an average of 7 years earlier than nonsmokers and were more than twice as likely to have AMI as nonsmokers in China. Smoking appeared to result in earlier infarction, especially ST elevated myocardial infarction in otherwise healthier patients who are likely to survive.