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Catharina von Nicolai, Åsa Ehlén, Juan S Martinez, Aura Carreira
Homologous recombination (HR) is an essential pathway to restart stalled replication forks, repair spontaneous DNA double-strand breaks, and generate genetic diversity. Together with genetic studies in model organisms, the development of purification protocols and biochemical assays has allowed investigators to begin to understand how the complex machinery of HR functions. At the core of the HR process is the recombination enzyme RecA in bacteria or RAD51 and DMC1 in eukaryotes. The main steps of HR can be reconstituted in vitro and involve: (1) The formation of a ssDNA-RAD51 complex into a helical structure termed the nucleoprotein filament after one DNA strand has been resected at the site of the break...
2018: Methods in Enzymology
Yuen-Ling Chan, Douglas K Bishop
Budding yeast Dmc1 is a member of the RecA family of strand exchange proteins essential for homologous recombination (HR) during meiosis. Dmc1 mediates the steps of homology search and DNA strand exchange reactions that are central to HR. To achieve optimum activity, Dmc1 requires a number of accessory factors. Although methods for purification of Dmc1 and many of its associated factors have been described (Binz, Dickson, Haring, & Wold, 2006; Busygina et al., 2013; Chan, Brown, Qin, Handa, & Bishop, 2014; Chi et al...
2018: Methods in Enzymology
J Brooks Crickard, Kyle Kaniecki, YoungHo Kwon, Patrick Sung, Michael Lisby, Eric C Greene
Most eukaryotes have two Rad51/RecA family recombinases, Rad51, which promotes recombination during mitotic double-strand break (DSB) repair, and the meiosis-specific recombinase Dmc1. During meiosis, the strand exchange activity of Rad51 is downregulated through interactions with the meiosis-specific protein Hed1, which helps ensure that strand exchange is driven by Dmc1 instead of Rad51. Hed1 acts by preventing Rad51 from interacting with Rad54, a cofactor required for promoting strand exchange during homologous recombination...
February 14, 2018: EMBO Journal
J Brooks Crickard, Kyle Kaniecki, YoungHo Kwon, Patrick Sung, Eric C Greene
During meiosis, the two DNA recombinases Rad51 and Dmc1, form specialized presynaptic filaments that are adapted for performing recombination between homologous chromosomes. There is currently a limited understanding of how these two recombinases are organized within the meiotic presynaptic filament. Here, we used single molecule imaging to examine the properties of presynaptic complexes comprised of both Rad51 and Dmc1. We demonstrate that Rad51 and Dmc1 have an intrinsic ability to self-segregate, even in the absence of any other recombination accessory proteins...
January 30, 2018: Journal of Biological Chemistry
Zhi-Hao Liu, Qi-Liang Chen, Qiang Chen, Fang Li, Ying-Wen Li
In fish, spermatogenesis and somatic growth are mainly regulated by hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-somatic (HPS) axes, respectively. Xenoestrogens have been reported to impair spermatogenesis in some fishes, and arrest somatic growth in some others, whereas, whether xenoestrogens are capable of disrupting spermatogenesis and somatic growth simultaneously in fish that exhibits sexual dimorphic growth is little known, and the underlying mechanisms remain poorly understood. In this study, male juveniles of yellow catfish (Pelteobagrus fulvidraco), which exhibits a sexual dimorphic growth that favors males, were exposed to diethylstilbestrol (DES) for 28 days...
January 16, 2018: Fish Physiology and Biochemistry
Wen-Bin He, Chao-Feng Tu, Qiang Liu, Lan-Lan Meng, Shi-Min Yuan, Ai-Xiang Luo, Fu-Sheng He, Juan Shen, Wen Li, Juan Du, Chang-Gao Zhong, Guang-Xiu Lu, Ge Lin, Li-Qing Fan, Yue-Qiu Tan
BACKGROUND: The genetic causes of the majority of male and female infertility caused by human non-obstructive azoospermia (NOA) and premature ovarian insufficiency (POI) with meiotic arrest are unknown. OBJECTIVE: To identify the genetic cause of NOA and POI in two affected members from a consanguineous Chinese family. METHODS: We performed whole-exome sequencing of DNA from both affected patients. The identified candidate causative gene was further verified by Sanger sequencing for pedigree analysis in this family...
January 13, 2018: Journal of Medical Genetics
Minli Yu, Yali Xu, Ming Li, Dongfeng Li, Yinglin Lu, Debing Yu, Wenxing Du
Bisphenol A (BPA) as an endocrine-disrupting chemical with weak estrogenic activity affects formation of primordial follicles. This study aimed to identify the potential effects and molecular mechanisms of BPA on meiosis and primordial follicle formation in chickens. The results suggest that the cortical layer was thickened and the number of germ cells that entered into meiosis was increased in BPA-treated ovaries. The percentage of γH2AX-positive cells increased significantly. In addition, up-regulated mRNA expression of meiotic genes, including stimulated by retinoic acid gene 8 (Stra8), disrupted meiotic cDNA 1 homologue (Dmc1) and synaptonemal complex protein 3 (Scp3) were observed in BPA-treated ovaries...
November 4, 2017: General and Comparative Endocrinology
Ryan Kniewel, Hajime Murakami, Yan Liu, Masaru Ito, Kunihiro Ohta, Nancy M Hollingsworth, Scott Keeney
Saccharomyces cerevisiae Mek1 is a CHK2/Rad53-family kinase that regulates meiotic recombination and progression upon its activation in response to DNA double-strand breaks (DSBs). The full catalog of direct Mek1 phosphorylation targets remains unknown. Here, we show that phosphorylation of histone H3 on threonine 11 (H3 T11ph) is induced by meiotic DSBs in S. cerevisiae and Schizosaccharomyces pombe Molecular genetic experiments in S. cerevisiae confirmed that Mek1 is required for H3 T11ph and revealed that phosphorylation is rapidly reversed when Mek1 kinase is no longer active...
December 2017: Genetics
Yaqin Wang, Yingwen Li, Qiliang Chen, Zhihao Liu
Diethylstilbestrol (DES), a non-steroidal estrogen, has been found to cause altered germ cell development and disordered ovarian development in fish females. However, the mechanisms that might be involved are poorly understood. In this study, female juveniles of yellow catfish (Pelteobagrus fulvidraco) (120 days post-hatching) were exposed to two doses (10 and 100 ng l(-1) ) of DES for 28 days. After the endpoint of exposure, decreased ovary weight and gonadosomatic index, as well as various ovarian impairments were observed in response to DES...
September 28, 2017: Journal of Applied Toxicology: JAT
Huei-Mei Hsieh, Mei-Chu Chung, Pao-Yang Chen, Fei-Man Hsu, Wen-Wei Liao, Ai-Ning Sung, Chun-Ru Lin, Chung-Ju Rachel Wang, Yu-Hsin Kao, Mei-Jane Fang, Chi-Yung Lai, Chieh-Chen Huang, Jyh-Ching Chou, Wen-Neng Chou, Bill Chia-Han Chang, Yu-Ming Ju
BACKGROUND: Termitomyces mushrooms are mutualistically associated with fungus-growing termites, which are widely considered to cultivate a monogenotypic Termitomyces symbiont within a colony. Termitomyces cultures isolated directly from termite colonies are heterokaryotic, likely through mating between compatible homokaryons. RESULTS: After pairing homokaryons carrying different haplotypes at marker gene loci MIP and RCB from a Termitomyces fruiting body associated with Odontotermes formosanus, we observed nuclear fusion and division, which greatly resembled meiosis, during each hyphal cell division and conidial formation in the resulting heterokaryons...
September 19, 2017: Botanical Studies (Taipei, Taiwan)
Anusha M Gopalakrishnan, Ahmed S I Aly, L Aravind, Nirbhay Kumar
In sexually reproducing organisms, meiosis is an essential step responsible for generation of haploid gametes from diploid somatic cells. The quest for understanding regulatory mechanisms of meiotic recombination in Plasmodium led to identification of a gene encoding a protein that contains 11 copies of C2H2 zinc fingers (ZnF). Reverse genetic approaches were used to create Plasmodium berghei parasites either lacking expression of full-length Plasmodium berghei zinc finger protein (PbZfp) (knockout [KO]) or expressing PbZfp lacking C-terminal zinc finger region (truncated [Trunc])...
August 29, 2017: MBio
Anura Shodhan, Maria Novatchkova, Josef Loidl
Meiotic recombination is initiated by DNA double-strand breaks (DSBs). Most DSBs are converted into nonreciprocal exchanges (gene conversions) or crossovers (COs) between sister chromatids. Only a minority of DSBs are processed toward interhomolog COs, the precursors of the chiasmata that connect homologous chromosomes. Dmc1, the meiosis-specific paralog of the universal recombination protein Rad51, is required for interhomolog COs; in its absence, univalents are primarily formed. Here, we report a ciliate-specific novel meiotic gene, BIME2, which also promotes interhomolog crossing over...
October 2017: Chromosome Research
Gunjita Singh, Olivier Da Ines, Maria Eugenia Gallego, Charles I White
The ploidy of eukaryote gametes must be halved to avoid doubling of numbers of chromosomes with each generation and this is carried out by meiosis, a specialized cell division in which a single chromosomal replication phase is followed by two successive nuclear divisions. With some exceptions, programmed recombination ensures the proper pairing and distribution of homologous pairs of chromosomes in meiosis and recombination defects thus lead to sterility. Two highly related recombinases are required to catalyse the key strand-invasion step of meiotic recombination and it is the meiosis-specific DMC1 which is generally believed to catalyse the essential non-sister chromatid crossing-over, with RAD51 catalysing sister-chromatid and non-cross-over events...
2017: PloS One
Wataru Kobayashi, Noriko Hosoya, Shinichi Machida, Kiyoshi Miyagawa, Hitoshi Kurumizaka
The synaptonemal complex is a higher-ordered proteinaceous architecture formed between homologous chromosomes. SYCP3 is a major component of the lateral/axial elements in the synaptonemal complex and is essential for meiotic recombination. Previous genetic studies showed that SYCP3 functions in meiotic homologous recombination biased to interhomologous chromosomes, by regulating the strand invasion activities of the RAD51 and DMC1 recombinases. However, the mechanism by which SYCP3 regulates RAD51- and DMC1-mediated strand invasion remains elusive...
September 2017: Genes to Cells: Devoted to Molecular & Cellular Mechanisms
Maria Spies
The exchange of DNA strands between broken and intact molecules lies at the heart of fundamental cellular processes ranging from repairing DNA damage by homologous recombination to generation of genetic diversity during sexual reproduction. New work by Lee and colleagues utilizes the DNA curtain method, an elegant single-molecule technique, to demonstrate common and idiosyncratic features in the DNA strand exchange mechanisms of three RecA-family recombinases, bacterial RecA, and eukaryotic Rad51 and Dmc1 proteins...
June 30, 2017: Journal of Biological Chemistry
Janeen Braynen, Yan Yang, Fang Wei, Gangqiang Cao, Gongyao Shi, Baoming Tian, Xiaowei Zhang, Hao Jia, Xiaochun Wei, Zhenzhen Wei
Polyploidy is a fundamental process in plant evolution. Understanding the polyploidy-associated effects on plant reproduction is essential for polyploid breeding program. In the present study, our cytological analysis firstly demonstrated that an overall course of meiosis was apparently distorted in the synthetic polyploid Brassica rapa in comparison with its diploid progenitor. To elucidate genetic basis of this irregular meiosis at a molecular level, the comparative RNA-seq analysis was further used to investigate differential genetic regulation of developing floral buds identified at meiosis between autotetraploid and diploid B...
2017: Frontiers in Plant Science
Kayleigh Wardell, Sam Haldenby, Nathan Jones, Susan Liddell, Greg H P Ngo, Thorsten Allers
Homologous recombination plays a central role in the repair of double-strand DNA breaks, the restart of stalled replication forks and the generation of genetic diversity. Regulation of recombination is essential since defects can lead to genome instability and chromosomal rearrangements. Strand exchange is a key step of recombination - it is catalysed by RecA in bacteria, Rad51/Dmc1 in eukaryotes and RadA in archaea. RadB, a paralogue of RadA, is present in many archaeal species. RadB has previously been proposed to function as a recombination mediator, assisting in RadA-mediated strand exchange...
July 2017: DNA Repair
P Sahin, N E Gungor-Ordueri, C Celik-Ozenci
Rapamycin (mTOR inhibitor) has been reported to have negative effect on human male gonadal function. Previously, we showed that mTOR signalling molecules are expressed during early spermatogenesis in mice. The objective of this study was to investigate the role of mTOR signalling in meiosis both during the first wave of spermatogenesis and also during adult spermatogenesis. Day 5 post-partum mice were administered rapamycin and retinoic acid (RA; a Stra8 activator), and expression of p-p70S6K and Stra8 proteins was evaluated...
May 10, 2017: Andrologia
Ja Yil Lee, Justin B Steinfeld, Zhi Qi, YoungHo Kwon, Patrick Sung, Eric C Greene
Homologous recombination plays key roles in double-strand break repair, rescue, and repair of stalled replication forks and meiosis. The broadly conserved Rad51/RecA family of recombinases catalyzes the DNA strand invasion reaction that takes place during homologous recombination. We have established single-stranded (ss)DNA curtain assays for measuring individual base triplet steps during the early stages of strand invasion. Here, we examined how base triplet stepping by RecA, Rad51, and Dmc1 is affected by DNA sequence imperfections, such as single and multiple mismatches, abasic sites, and single nucleotide insertions...
June 30, 2017: Journal of Biological Chemistry
Stephanie Schubert, Tim Ripperger, Melanie Rood, Anthony Petkidis, Winfried Hofmann, Hildegard Frye-Boukhriss, Marcel Tauscher, Bernd Auber, Ursula Hille-Betz, Thomas Illig, Brigitte Schlegelberger, Doris Steinemann
GT198, located 470 kb downstream of BRCA1, encodes for the nuclear PSMC3-interacting protein, which functions as co-activator of steroid hormone-mediated gene expression, and is involved in RAD51 and DMC1-mediated homologous recombination during DNA repair of double-strand breaks. Recently, germline variants in GT198 have been identified in hereditary breast and ovarian cancer (HBOC) patients, mainly in cases with early-onset. We screened a cohort of 166 BRCA1/2 mutation-negative HBOC patients, of which 56 developed early-onset breast cancer before the age of 36 years, for GT198 variants...
January 2017: Genes & Cancer
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