Determining the kinetics of break-induced replication (BIR) by the assay for monitoring BIR elongation rate (AMBER)

Identification of the nuclear localization signal in the Saccharomyces cerevisiae Pif1 DNA helicase

Saccharomyces cerevisiae Pif1 is a multi-functional DNA helicase that plays diverse roles in the maintenance of the nuclear and mitochondrial genomes. Two isoforms of Pif1 are generated from a single open reading frame by the use of alternative translational start sites. The Mitochondrial Targeting Signal (MTS) of Pif1 is located between the two start sites, but a Nuclear Localization Signal (NLS) has not been identified. Here we used sequence and functional analysis to identify an NLS element. A mutant allele of PIF1 (pif1-NLSΔ) that lacks four basic amino acids (781KKRK784) in the carboxyl-terminal domain of the 859 amino acid Pif1 was expressed at wild type levels and retained wild type mitochondrial function. However, pif1-NLSΔ cells were defective in four tests for nuclear function: telomere length maintenance, Okazaki fragment processing, break-induced replication (BIR), and binding to nuclear target sites. Fusing the NLS from the simian virus 40 (SV40) T-antigen to the Pif1-NLSΔ protein reduced the nuclear defects of pif1-NLSΔ cells. Thus, four basic amino acids near the carboxyl end of Pif1 are required for the vast majority of nuclear Pif1 function. Our study also reveals phenotypic differences between the previously described loss of function pif1-m2 allele and three other pif1 mutant alleles generated in this work, which will be useful to study nuclear Pif1 functions.

Traditional Chinese medicine for heart failure with preserved ejection fraction: clinical evidence and potential mechanisms

Heart failure with preserved ejection fraction accounts for a large proportion of heart failure, and it is closely related to a high hospitalization rate and high mortality rate of cardiovascular disease. Although the methods and means of modern medical treatment of HFpEF are becoming increasingly abundant, they still cannot fully meet the clinical needs of HFpEF patients. Traditional Chinese medicine is an important complementary strategy for the treatment of diseases in modern medicine, and it has been widely used in clinical research on HFpEF in recent years. This article reviews the current situation of HFpEF management, the evolution of guidelines, the clinical evidence and the mechanism of TCM in the treatment of HFpEF. The purpose of this study is to explore the application of TCM for HFpEF, to further improve the clinical symptoms and prognosis of patients and to provide a reference for the diagnosis and treatment of the disease.

Break-induced replication: unraveling each step

Break-induced replication (BIR) repairs one-ended double-strand DNA breaks through invasion into a homologous template followed by DNA synthesis. Different from S-phase replication, BIR copies the template DNA in a migrating displacement loop (D-loop) and results in conservative inheritance of newly synthesized DNA. This unusual mode of DNA synthesis makes BIR a source of various genetic instabilities like those associated with cancer in humans. This review focuses on recent progress in delineating the mechanism of Rad51-dependent BIR in budding yeast. In addition, we discuss new data that describe changes in BIR efficiency and fidelity on encountering replication obstacles as well as the implications of these findings for BIR-dependent processes such as telomere maintenance and the repair of collapsed replication forks.