Structures of pMV158 replication initiator RepB with and without DNA reveal a flexible dual-function protein.

DNA replication is essential to all living organisms as it ensures the fidelity of genetic material for the next generation of dividing cells. One of the simplest replication initiation mechanisms is the rolling circle replication. In the streptococcal plasmid pMV158, which confers antibiotic resistance to tetracycline, replication initiation is catalysed by RepB protein. The RepB N-terminal domain or origin binding domain binds to the recognition sequence (bind locus) of the double-strand origin of replication and cleaves one DNA strand at a specific site within the nic locus. Using biochemical and crystallographic analyses, here we show how the origin binding domain recognises and binds to the bind locus using structural elements removed from the active site, namely the recognition α helix, and a ß-strand that organises upon binding. A new hexameric structure of full-length RepB that highlights the great flexibility of this protein is presented, which could account for its ability to perform different tasks, namely bind to two distinct loci and cleave one strand of DNA at the plasmid origin.

Oral health after breast cancer treatment in postmenopausal women.

OBJECTIVE: Oral health can affect a patient's general health and quality of life. Given the increase in breast cancer survival rates, investigations of factors influencing the quality of life of survivors have gained importance. Therefore, the objective of our study was to characterize oral health in postmenopausal breast cancer survivors. METHODS: We conducted a matched case-control study. Forty-eight women who survived breast cancer (age 62.1±9.1 years) and 48 healthy controls (age 61.8±8.6 years) were included. For each case and control, a complete oral evaluation chart was completed. RESULTS: The prevalence of chronic periodontal disease was 98% in breast cancer survivors and 87% in controls. The breast cancer survivors had a median of 16 remaining teeth, whereas controls had a median of 22 remaining teeth (p = 0.03). The percentage of sites with gingival bleeding was 16.05% (0-100%) in breast cancer survivors and 0% (0-72%) in controls (p = 0.04). CONCLUSION: Chronic periodontal disease and tooth loss were highly prevalent in postmenopausal breast cancer survivors. To improve survivors' quality of life, a preventive oral health evaluation should be available prior to cancer treatment.