Mutational analysis of Mei5, a subunit of Mei5-Sae3 complex, in Dmc1-mediated recombination during yeast meiosis.

Interhomolog recombination in meiosis is mediated by the Dmc1 recombinase. The Mei5-Sae3 complex of Saccharomyces cerevisiae promotes Dmc1 assembly and functions with Dmc1 for homology-mediated repair of meiotic DNA double-strand breaks. How Mei5-Sae3 facilitates Dmc1 assembly remains poorly understood. In this study, we created and characterized several mei5 mutants featuring the amino acid substitutions of basic residues. We found that Arg97 of Mei5, conserved in its ortholog, SFR1 (complex with SWI5), RAD51 mediator, in humans and other organisms, is critical for complex formation with Sae3 for Dmc1 assembly. Moreover, the substitution of either Arg117 or Lys133 with Ala in Mei5 resulted in the production of a C-terminal truncated Mei5 protein during yeast meiosis. Notably, the shorter Mei5-R117A protein was observed in meiotic cells but not in mitotic cells when expressed, suggesting a unique regulation of Dmc1-mediated recombination by posttranslational processing of Mei5-Sae3.

DNA double-strand breaks regulate the cleavage-independent release of Rec8-cohesin during yeast meiosis.

The mitotic cohesin complex necessary for sister chromatid cohesion and chromatin loop formation shows local and global association to chromosomes in response to DNA double-strand breaks (DSBs). Here, by genome-wide binding analysis of the meiotic cohesin with Rec8, we found that the Rec8-localization profile along chromosomes is altered from middle to late meiotic prophase I with cleavage-independent dissociation. Each Rec8-binding site on the chromosome axis follows a unique alternation pattern with dissociation and probably association. Centromeres showed altered Rec8 binding in late prophase I relative to mid-prophase I, implying chromosome remodeling of the regions. Rec8 dissociation ratio per chromosome is correlated well with meiotic DSB density. Indeed, the spo11 mutant deficient in meiotic DSB formation did not change the distribution of Rec8 along chromosomes in late meiotic prophase I. These suggest the presence of a meiosis-specific regulatory pathway for the global binding of Rec8-cohesin in response to DSBs.

The role of conserved amino acid residues of Sae3 in Mei5-Sae3 complex for Dmc1 assembly in meiotic recombination.

Meiotic recombination between homologous chromosomes is promoted by the collaborative action of two RecA homologs, Rad51 and meiosis-specific Dmc1. The filament assembly of Dmc1 is promoted by meiosis-specific Mei5-Sae3 in budding yeast. Mei5-Sae3 shows sequence similarity to fission yeast Sfr1-Swi5, which stimulates DNA strand exchanges by Rad51 as well as Dmc1. Sae3 and Swi5 share a conserved motif with the amino acid sequence YNEI/LK/RD. In this study, we analyzed the role of the YNEL residues in the Sae3 sequence in meiotic recombination and found that these residues are critical for Sae3 function in Dmc1 assembly. L59 substitution in the Sae3 protein disrupts complex formation with Mei5, while Y56 and N57 substitutions do not. These observations reveal the differential contribution of conserved YNEL residues to Sae3 activities in meiotic recombination.

In silico structural and functional prediction of African swine fever virus protein-B263R reveals features of a TATA-binding protein.

African swine fever virus (ASFV) is the etiological agent of ASF, a fatal hemorrhagic fever that affects domestic pigs. There is currently no vaccine against ASFV, making it a significant threat to the pork industry. The ASFV genome sequence has been published; however, about half of ASFV open reading frames have not been characterized in terms of their structure and function despite being essential for our understanding of ASFV pathogenicity. The present study reports the three-dimensional structure and function of uncharacterized protein, pB263R (NP_042780.1), an open reading frame found in all ASFV strains. Sequence-based profiling and hidden Markov model search methods were used to identify remote pB263R homologs. Iterative Threading ASSEmbly Refinement (I-TASSER) was used to model the three-dimensional structure of pB263R. The posterior probability of fold family assignment was calculated using TM-fold, and biological function was assigned using TM-site, RaptorXBinding, Gene Ontology, and TM-align. Our results suggests that pB263R has the features of a TATA-binding protein and is thus likely to be involved in viral gene transcription.