Homologous recombination (HR) is a double-strand break DNA repair pathway that preserves chromosome structure. To repair damaged DNA, HR uses an intact donor DNA sequence located elsewhere in the genome. After the double-strand break is repaired, DNA sequence information can be transferred between donor and recipient DNA molecules through different mechanisms, including DNA crossovers that form between homologous chromosomes. Regulation of DNA sequence transfer is an important step in effectively completing HR and maintaining genome integrity. For example, mitotic exchange of information between homologous chromosomes can result in loss-of-heterozygosity (LOH), and in higher eukaryotes, the development of cancer. The DNA motor protein Rdh54 is a highly conserved DNA translocase that functions during HR. Several existing phenotypes in rdh54Δ strains suggest that Rdh54 may regulate effective exchange of DNA during HR. In our current study, we used a combination of biochemical and genetic techniques to dissect the role of Rdh54 on the exchange of genetic information during DNA repair. Our data indicate that RDH54 regulates DNA strand exchange by stabilizing Rad51 at an early HR intermediate called the displacement loop (D-loop). Rdh54 acts in opposition to Rad51 removal by the DNA motor protein Rad54. Furthermore, we find that expression of a catalytically inactivate allele of Rdh54, rdh54K318R, favors non-crossover outcomes. From these results, we propose a model for how Rdh54 may kinetically regulate strand exchange during homologous recombination.

OBJECTIVE: Very few studies have addressed attitudes on posthumous sperm retrieval due to the ethical and legal ramifications of the use of gametes after death. We evaluated the presence and content of a policy on posthumous sperm retrieval at the 50 major academic medical centers.DESIGN: Questionnaire based telephone study / web survey. MATERIALS AND METHODS: We surveyed the 50 major academic medical centers as ranked for research in 2016 by U.S. News & World Report. We gathered data on presence and content of posthumous sperm retrieval policies. If not published, we contacted the legal counsel for the medical center, the ethics and compliance offices, as well as the Urology Department for each center.RESULTS: Out of the 50 major academic medical centers, we gathered data on posthumous sperm retrieval from 14 (28%). Of the 14 institutions, five (35.7%) had policies regarding posthumous sperm retrieval and the remaining nine (64.3%) did not have a policy. Four of the nine medical centers without policies have discussed development of a policy but did not formalize it due to lack of legal guidance as a barrier to policy adoption. Out of the five centers that had a policy, one required prior written consent, while four allowed for verbal or inferred consent from the surviving life partner.CONCLUSIONS: Very few, less than 1/3, of the surveyed academic medical centers have policies on posthumous sperm retrieval. Medical centers can adopt individualized policies based on guidelines published by the American Society for Reproductive Medicine.

Rdh54 is a conserved DNA translocase that participates in homologous recombination (HR), DNA checkpoint adaptation, and chromosome segregation. Saccharomyces cerevisiae Rdh54 is a known target of the Mec1/Rad53 signaling axis, which globally protects genome integrity during DNA metabolism. While phosphorylation of DNA repair proteins by Mec1/Rad53 is critical for HR progression little is known about how specific post translational modifications alter HR reactions. Phosphorylation of Rdh54 is linked to protection of genomic integrity but the consequences of modification remain poorly understood. Here, we demonstrate that phosphorylation of the Rdh54 C-terminus by the effector kinase Rad53 down regulates Rdh54 activity resulting in a 50% decrease in translocation velocity on dsDNA as revealed by single molecule imaging. Genetic assays reveal that loss of phosphorylation reduces interhomolog gene conversion, increases break induced replication, and decreases crossover outcomes. Our data highlight Rad53 as a key regulator of HR intermediates through activation and attenuation of Rdh54 motor function.