Histone H2AX has a role in suppressing genomic instability and cancer. However, the mechanisms by which it performs these functions are poorly understood. After DNA breakage, H2AX is phosphorylated on serine 139 in chromatin near the break. We show here that H2AX serine 139 enforces efficient homologous recombinational repair of a chromosomal double-strand break (DSB) by using the sister chromatid as a template. BRCA1, Rad51, and CHK2 contribute to recombinational repair, in part independently of H2AX. H2AX(-/-) cells show increased use of single-strand annealing, an error-prone deletional mechanism of DSB repair. Therefore, the chromatin response around a chromosomal DSB, in which H2AX serine 139 phosphorylation plays a central role, "shapes" the repair process in favor of potentially error-free interchromatid homologous recombination at the expense of error-prone repair. H2AX phosphorylation may help set up a favorable disposition between sister chromatids.

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The abrasion of the outer insulation in the IP of silicone leads was significant regardless of the level of degradation and is associated with IE. The abrasions observed in the IP of the leads were similar to those observed in the intravenous and pocket parts, with predomination of the third level of degradation. There was an association between the presence of any abrasion in the IP of the leads and the number of leads, and in the case of atrial leads between abrasions and fixation type, dwell time, and number of procedures until explantation.

Abstract. Floristic studies were carried out in NE Poland in [2007][2008] in three types of railway areas: operating tracks, tracks abandoned less than 10 years ago, and tracks abandoned more than 10 years ago. In the 41 sections of railway tracks surveyed, 338 species were recorded, including 22 species that occurred at > 50% frequency, 27 species strongly associated with operating railway areas, and 4 species typical of railway areas in Poland. Comparative analysis of the flora of the 3 types of railway areas investigated showed significant differences in the richness and structure of their floras.