Characterization of factors that underlie transcriptional silencing in C. elegans oocytes.

While it has been appreciated for decades that prophase-arrested oocytes are transcriptionally silenced on a global level, the molecular pathways that promote silencing have remained elusive. Previous work in C. elegans has shown that both topoisomerase II (TOP-2) and condensin II collaborate with the H3K9me heterochromatin pathway to silence gene expression in the germline during L1 starvation, and that the PIE-1 protein silences the genome in the P-lineage of early embryos. Here, we show that all three of these silencing systems, TOP-2/condensin II, H3K9me, and PIE-1, are required for transcriptional repression in oocytes. We find that H3K9me3 marks increase dramatically on chromatin during silencing, and that silencing is under cell cycle control. We also find that PIE-1 localizes to the nucleolus just prior to silencing, and that nucleolar dissolution during silencing is dependent on TOP-2/condensin II. Our data identify both the molecular components and the trigger for genome silencing in oocytes and establish a link between PIE-1 nucleolar residency and its ability to repress transcription.

Assessment of attitude towards COVID-19 vaccine and associated factors among clinical practitioners in Ethiopia: A cross-sectional study.

BACKGROUND: Clinical practitioners are influential figures in the public's health-seeking behavior. Therefore, understanding their attitudes toward the COVID-19 vaccine is critical for implementing successful vaccination programs. Our study aimed to investigate clinical practitioners' acceptance of the COVID-19 vaccine and associated factors for evidence-based interventions. METHODS: Data from 461 clinical practitioners were collected using a cross-sectional design via an online self-administered survey. Descriptive and multiple logistic regression analyses and chi-square tests were conducted using R version 3.6.1. RESULTS: The COVID-19 vaccine was accepted by 84.4 percent of those polled, and 86.1 percent said they would recommend it to others. Individuals with advanced levels of education demonstrated greater readiness for vaccine acceptance (P<0.001) and willingness to recommend (P<0.001). On the other hand, practitioners with concerns about the safety of vaccines developed in emergency settings were less likely to accept vaccines (OR = 0.22). Practitioners influenced by social media posts (OR = 0.91) and religious beliefs (OR = 0.71) were found to be less willing to recommend the vaccine. CONCLUSION: The study demonstrated that interventions to improve clinical practitioners' acceptance and recommendation of the COVID-19 vaccine should consider the following factors: level of experience and education, religious beliefs, safety concerns, specific profession, and source of information. Vaccine literacy efforts that directly address specific concerns and misconceptions, such as those that reconcile social media information and religious beliefs with scientific literature, are recommended.

A global chromatin compaction pathway that represses germline gene expression during starvation.

While much is known about how transcription is controlled at individual genes, comparatively little is known about how cells regulate gene expression on a genome-wide level. Here, we identify a molecular pathway in the C. elegans germline that controls transcription globally in response to nutritional stress. We report that when embryos hatch into L1 larvae, they sense the nutritional status of their environment, and if food is unavailable, they repress gene expression via a global chromatin compaction (GCC) pathway. GCC is triggered by the energy-sensing kinase AMPK and is mediated by a novel mechanism that involves the topoisomerase II/condensin II axis acting upstream of heterochromatin assembly. When the GCC pathway is inactivated, then transcription persists during starvation. These results define a new mode of whole-genome control of transcription.

Cells deficient for Krüppel-like factor 4 exhibit mitochondrial dysfunction and impaired mitophagy.

Krüppel-like factor 4 (Human Protein: KLF4; Human Gene: Klf4; Murine Protein: KLF4; Murine Gene: Klf4) is a zinc finger-containing transcription factor with diverse regulatory functions. Mouse embryonic fibroblasts (MEFs) lacking Klf4 exhibit genomic instability, increased reactive oxygen species (ROS), and decreased autophagy. Elevated ROS is linked to impairments in mitochondrial damage recovery responses and is often tied to disruption in mitochondrial-targeted autophagy known as mitophagy. In this study, we sought to identify a mechanistic connection between KLF4 and mitophagy. Using flow cytometry, we found that Klf4-null MEFs have diminished ability to recover mitochondrial health and regulate ROS levels after mitochondrial damage. Confocal microscopy indicated decreased localization of autophagy protein LC3 to mitochondria following mitochondrial damage in Klf4-null cells, suggesting decreased mitophagy. Western blotting and RT-PCR revealed decreased mRNA and protein expression of the mitophagy-associated protein Bnip3 and antioxidant protein GSTα4 in Klf4-null cells, providing a rationale for their impaired mitophagy and ROS accumulation. Inducing Bnip3 expression in these cells recovered mitophagy but did not decrease ROS accumulation. Our findings suggest that in Klf4-null cells, decreased Bnip3 expression impairs mitophagy and is associated with increased mitochondrial ROS production after mitochondrial damage, providing a rationale for their genomic instability and supports a tumor suppressive role for KLF4 in certain tumors as previously observed.

Programmed DNA Breaks Activate the Germline Genome in Caenorhabditis elegans.

In Caenorhabditis elegans, the primordial germ cells Z2 and Z3 are born during early embryogenesis and then held in a transcriptionally quiescent state where the genome is highly compacted. When hatched L1s feed, the germline genome decompacts, and RNAPII is abruptly and globally activated. A previously documented yet unexplained feature of germline genome activation in the worm is the appearance of numerous DNA breaks coincident with RNAPII transcription. Here, we show that the DNA breaks are induced by topoisomerase II and that they function to recruit the RUVB complex to chromosomes so that RUVB can decompact the chromatin. DNA break- and RUVB-mediated decompaction is required for zygotic genome activation. This work highlights the importance of global chromatin decompaction in the rapid induction of gene expression and shows that one way cells achieve global decompaction is through programmed DNA breaks.