The Xer activation factor of TLCΦ expands the possibilities for Xer recombination

ABSTRACTMany mobile elements take advantage of the highly-conserved chromosome dimer resolution system of bacteria, Xer. They participate in the transmission of antibiotic resistance and pathogenicity determinants. In particular, the toxin-linked cryptic satellite phage (TLCΦ) plays an essential role in the continuous emergence of new toxigenic clones of the Vibrio cholerae strain at the origin of the ongoing 7th cholera pandemic. The Xer machinery is composed of two chromosomally-encoded tyrosine recombinases, XerC and XerD. They resolve chromosome dimers by adding a crossover between sister copies of a specific 28 base pair site of bacterial chromosomes, dif. The activity of XerD depends on a direct contact with a cell division protein, FtsK, which spatially and temporally constrains the process. TLCΦ encodes for a XerD-activation factor (XafT), which drives the integration of the phage into the dif site of the primary chromosome of V. cholerae independently of FtsK. However, XerD does not bind to the attachment site (attP) of TLCΦ, which raised questions on the integration process. Here, we compared the integration efficiency of thousands of synthetic mini-TLCΦ plasmids harbouring different attP sites and assessed their stability in vivo. In addition, we compared the efficiency with which XafT and the XerD activation domain of FtsK drive recombination reactions in vitro. Taken together, our results suggest that XafT promotes the formation of synaptic complexes between canonical Xer recombination sites and imperfect sites.

Shrimp Plasma CREG Is a Hemocyte Activation Factor

Cytokines are a class of immunoregulatory proteins that are secreted by cells. Although vertebrate cytokine, especially mammalian cytokine has been well studied for the past decades. Much less attention has been paid to invertebrate so that only some cytokines have been identified in invertebrates. We have chosen Peaneus vannamei as a model to explore novel invertebrate cytokines. To achieve this, we previously purified shrimp plasma low abundance proteins and identified more than 400 proteins with proteomics analyses. In this study, a cellular repressor of E1A-stimulated gene (CREG)-like protein, which is highly conserved from Drosophila melanogaster to Homo sapiens, was further characterized in shrimp plasma. We found that shrimp plasma CREG was a glycoprotein which was strongly induced in hemolymph at 8 h post-LPS injection. Further function experiment unveiled that recombinant shrimp CREG protein injection significantly increased phagocytic hemocyte and lysosome-high hemocyte proportion in hemolymph. After that, hemocytes from rEGFP- and rCREG-protein injected shrimps were subjected to transcriptome analyses, which revealed that shrimp CREG protein could comprehensively promote hemocyte maturation and activation. Taken together, our data clearly indicated that shrimp plasma CREG protein is a novel hemocyte activation factor, which is probably a conserved myeloid cell lineage activation factor from invertebrate to vertebrate.

A Novel Assisted Oocyte Activation Method Improves Fertilization in Patients With Recurrent Fertilization Failure

Total fertilization failure (TFF) occurs in 1–3% of total intracytoplasmic sperm injection (ICSI) cycles and can reoccur in subsequent cycles. Despite the high success rate with the application of assisted oocyte activation (AOA), there is still a small number of couples who cannot obtain fertilized eggs after conventional calcium (Ca2+) ionophores-based ICSI-AOA. Six couples experiencing repeated TFF or low fertilization (<10%) after ICSI and conventional ICSI-AOA were enrolled in this study. Compared with the regular ICSI group and the conventional ICSI-AOA group, the new AOA method, a combination of cycloheximide (CHX) and ionomycin, can significantly increase the fertilization rate from less than 10 up to approximately 50% in most cases. The normal distribution of sperm-related oocyte activation factor phospholipase C zeta (PLCζ1) in the sperms of the cases indicated the absence of an aberrant Ca2+ signaling activation. The results of the whole-embryo aneuploidies analysis indicated that oocytes receiving the novel AOA treatment had the potential to develop into blastocysts with normal karyotypes. Our data demonstrated that CHX combined with ionomycin was able to effectively improve the fertilization rate in the majority of patients suffering from TFF. This novel AOA method had a potential therapeutic effect on those couples experiencing TFF, even after conventional AOA, which may surmount the severe fertilization deficiencies in patients with a repeated low fertilization or TFF.

Determining Factors Affecting Fire Risk in a Hospital in Qazvin, Iran

Background: Hospitals are highly vulnerable to fire because of the presence of vulnerable people (patients, medical staff, and visitors), expensive equipment, and the ignorance and low-risk perception of occupants. Injuries caused by fire can result in life and financial losses and can disrupt the performance of a hospital. Fire risk assessment is an effective way to assess vulnerability, capacity, and capability. This study aims to evaluate the risk of fire and identify the effective factors and their contribution to a hospital. Materials and Methods: This cross-sectional study was conducted using the Fire Risk Assessment Method for Engineering (FRAME) in the equipment room of a hospital in Qazvin, Iran. The fire risk was first calculated by using the related formulas in Excel software. Then, the influential factors and their contribution to the overall risk were determined to perform corrective measures for reducing the risk. Results: The numerical value of risk for the building and its contents, occupants, and activities were 2.075, 3.315, and 2.481, respectively (>1), indicating its unacceptable level. Factors affecting the potential risk level for the building and its content and occupants were fire load, venting, and access. Regarding the acceptable risk level, the activation factor was identified as an influential factor in all domains. The highest contribution in the potential risk level for the building and its content and occupants was related to the fire load factor (1.6). In the acceptable risk level, the highest contribution was related to the activation factor (0.4). Conclusion: The FRAME method can also identify effective factors and their contribution to the overall fire risk of medical centers such as hospitals to help develop plans and special measures to reduce the risk.

Molecular Topology of RNA Polymerase I Upstream Activation Factor

ABSTRACT Upstream activation factor (UAF) is a multifunctional transcription factor in Saccharomyces cerevisiae that plays dual roles in activating RNA polymerase I (Pol I) transcription and repression of Pol II. For Pol I, UAF binds to a specific upstream element in the ribosomal DNA (rDNA) promoter and interacts with two other Pol I initiation factors, the TATA-binding protein (TBP) and core factor (CF). We used an integrated combination of chemical cross-linking mass spectrometry (CXMS), molecular genetics, protein biochemistry, and structural modeling to understand the topological framework responsible for UAF complex formation. Here, we report the molecular topology of the UAF complex, describe new structural and functional domains that play roles in UAF complex integrity, assembly, and biological function, and provide roles for previously identified UAF domains that include the Rrn5 SANT and histone fold domains. We highlight the role of new domains in Uaf30 that include an N-terminal winged helix domain and a disordered tethering domain as well as a BORCS6-like domain found in Rrn9. Together, our results reveal a unique network of topological features that coalesce around a histone tetramer-like core to form the dual-function UAF complex.