Polycomb Repressive Complex 2 Methylates Elongin A to Regulate Transcription.

Polycomb repressive complex 2 (PRC2-EZH2) methylates histone H3 at lysine 27 (H3K27) and is required to maintain gene repression during development. Misregulation of PRC2 is linked to a range of neoplastic malignancies, which is believed to involve methylation of H3K27. However, the full spectrum of non-histone substrates of PRC2 that might also contribute to PRC2 function is not known. We characterized the target recognition specificity of the PRC2 active site and used the resultant data to screen for uncharacterized potential targets. The RNA polymerase II (Pol II) transcription elongation factor, Elongin A (EloA), is methylated by PRC2 in vivo. Mutation of the methylated EloA residue decreased repression of a subset of PRC2 target genes as measured by both steady-state and nascent RNA levels and perturbed embryonic stem cell differentiation. We propose that PRC2 modulates transcription of a subset of low expression target genes in part via methylation of EloA.

Elongin A regulates transcription in vivo through enhanced RNA polymerase processivity.

Elongin is an RNA polymerase II (RNAPII)-associated factor that has been shown to stimulate transcriptional elongation in vitro. The Elongin complex is thought to be required for transcriptional induction in response to cellular stimuli and to ubiquitinate RNAPII in response to DNA damage. Yet, the impact of the Elongin complex on transcription in vivo has not been well studied. Here, we performed comprehensive studies of the role of Elongin A, the largest subunit of the Elongin complex, on RNAPII transcription genome-wide. Our results suggest that Elongin A localizes to actively transcribed regions and potential enhancers, and the level of recruitment correlated with transcription levels. We also identified a large group of factors involved in transcription as Elongin A-associated factors. In addition, we found that loss of Elongin A leads to dramatically reduced levels of serine2-phosphorylated, but not total, RNAPII, and cells depleted of Elongin A show stronger promoter RNAPII pausing, suggesting that Elongin A may be involved in the release of paused RNAPII. Our RNA-seq studies suggest that loss of Elongin A did not alter global transcription, and unlike prior in vitro studies, we did not observe a dramatic impact on RNAPII elongation rates in our cell-based nascent RNA-seq experiments upon Elongin A depletion. Taken together, our studies provide the first comprehensive analysis of the role of Elongin A in regulating transcription in vivo. Our studies also revealed that unlike prior in vitro findings, depletion of Elongin A has little impact on global transcription profiles and transcription elongation in vivo.

Elongin A associates with actively transcribed genes and modulates enhancer RNA levels with limited impact on transcription elongation rate in vivo.

Elongin A (EloA) is an essential transcription factor that stimulates the rate of RNA polymerase II (Pol II) transcription elongation in vitro. However, its role as a transcription factor in vivo has remained underexplored. Here we show that in mouse embryonic stem cells, EloA localizes to both thousands of Pol II transcribed genes with preference for transcription start site and promoter regions and a large number of active enhancers across the genome. EloA deletion results in accumulation of transcripts from a subset of enhancers and their adjacent genes. Notably, EloA does not substantially enhance the elongation rate of Pol II in vivo. We also show that EloA localizes to the nucleoli and associates with RNA polymerase I transcribed ribosomal RNA gene, Rn45s. EloA is a highly disordered protein, which we demonstrate forms phase-separated condensates in vitro, and truncation mutations in the intrinsically disordered regions (IDR) of EloA interfere with its targeting and localization to the nucleoli. We conclude that EloA broadly associates with transcribed regions, tunes RNA Pol II transcription levels via impacts on enhancer RNA synthesis, and interacts with the rRNA producing/processing machinery in the nucleolus. Our work opens new avenues for further investigation of the role of this functionally multifaceted transcription factor in enhancer and ribosomal RNA biology.

Anosmia as a prominent symptom of COVID-19 infection.

According to WHO recommendations, everyone must protect themselves against Coronavirus disease 2019 (COVID-19), which will also protect others. Due to the lack of current effective treatment and vaccine for COVID-19, screening, rapid diagnosis and isolation of the patients are essential (1, 2). Therefore, identifying the early symptoms of COVID-19 is of particular importance and is a health system priority. Early studies from COVID-19 outbreak in China have illustrated several non-specific signs and symptoms in infected patients, including fever, dry cough, dyspnea, myalgia, fatigue, lymphopenia, and radiographic evidence of pneumonia (3, 4). Recently, a probability of association between COVID-19 and altered olfactory function has been reported in South Korea, Iran, Italy, France, UK and the United States (5-8). However, to our knowledge, the definite association between COVID-19 and anosmia has not been published.

Drosophila Set1 is the major histone H3 lysine 4 trimethyltransferase with role in transcription.

Histone H3 lysine 4 trimethylation (H3K4me3) is a major hallmark of promoter-proximal histones at transcribed genes. Here, we report that a previously uncharacterized Drosophila H3K4 methyltransferase, dSet1, and not the other putative histone H3K4 methyltransferases (Trithorax; Trithorax-related protein), is predominantly responsible for histone H3K4 trimethylation. Functional and proteomics studies reveal that dSet1 is a component of a conserved H3K4 trimethyltransferase complex and polytene staining and live cell imaging assays show widespread association of dSet1 with transcriptionally active genes. dSet1 is present at the promoter region of all tested genes, including activated Hsp70 and Hsp26 heat shock genes and is required for optimal mRNA accumulation from the tested genes. In the case of Hsp70, the mRNA production defect in dSet1 RNAi-treated cells is accompanied by retention of Pol II at promoters. Our data suggest that dSet1-dependent H3K4me3 is responsible for the generation of a chromatin structure at active promoters that ensures optimal Pol II release into productive elongation.

Defining mechanisms that regulate RNA polymerase II transcription in vivo.

In the eukaryotic genome, the thousands of genes that encode messenger RNA are transcribed by a molecular machine called RNA polymerase II. Analysing the distribution and status of RNA polymerase II across a genome has provided crucial insights into the long-standing mysteries of transcription and its regulation. These studies identify points in the transcription cycle where RNA polymerase II accumulates after encountering a rate-limiting step. When coupled with genome-wide mapping of transcription factors, these approaches identify key regulatory steps and factors and, importantly, provide an understanding of the mechanistic generalities, as well as the rich diversities, of gene regulation.

Spt6 enhances the elongation rate of RNA polymerase II in vivo.

Several eukaryotic transcription factors have been shown to modulate the elongation rate of RNA polymerase II (Pol II) on naked or chromatin-reconstituted templates in vitro. However, none of the tested factors have been shown to directly affect the elongation rate of Pol II in vivo. We performed a directed RNAi knock-down (KD) screen targeting 141 candidate transcription factors and identified multiple factors, including Spt6, that alter the induced Hsp70 transcript levels in Drosophila S2 cells. Spt6 is known to interact with both nucleosome structure and Pol II, and it has properties consistent with having a role in elongation. Here, ChIP assays of the first wave of Pol II after heat shock in S2 cells show that KD of Spt6 reduces the rate of Pol II elongation. Also, fluorescence recovery after photobleaching assays of GFP-Pol II in salivary gland cells show that this Spt6-dependent effect on elongation rate persists during steady-state-induced transcription, reducing the elongation rate from approximately 1100 to 500 bp/min. Furthermore, RNAi depletion of Spt6 reveals its broad requirement during different stages of development.

lncRNA DIGIT and BRD3 protein form phase-separated condensates to regulate endoderm differentiation.

Cooperation between DNA, RNA and protein regulates gene expression and controls differentiation through interactions that connect regions of nucleic acids and protein domains and through the assembly of biomolecular condensates. Here, we report that endoderm differentiation is regulated by the interaction between the long non-coding RNA (lncRNA) DIGIT and the bromodomain and extraterminal domain protein BRD3. BRD3 forms phase-separated condensates of which the formation is promoted by DIGIT, occupies enhancers of endoderm transcription factors and is required for endoderm differentiation. BRD3 binds to histone H3 acetylated at lysine 18 (H3K18ac) in vitro and co-occupies the genome with H3K18ac. DIGIT is also enriched in regions of H3K18ac, and the depletion of DIGIT results in decreased recruitment of BRD3 to these regions. Our findings show that cooperation between DIGIT and BRD3 at regions of H3K18ac regulates the transcription factors that drive endoderm differentiation and suggest that protein-lncRNA phase-separated condensates have a broader role as regulators of transcription.

Drosophila Paf1 modulates chromatin structure at actively transcribed genes.

The Paf1 complex in yeast has been reported to influence a multitude of steps in gene expression through interactions with RNA polymerase II (Pol II) and chromatin-modifying complexes; however, it is unclear which of these many activities are primary functions of Paf1 and are conserved in metazoans. We have identified and characterized the Drosophila homologs of three subunits of the yeast Paf1 complex and found striking differences between the yeast and Drosophila Paf1 complexes. We demonstrate that although Drosophila Paf1, Rtf1, and Cdc73 colocalize broadly with actively transcribing, phosphorylated Pol II, and all are recruited to activated heat shock genes with similar kinetics; Rtf1 does not appear to be a stable part of the Drosophila Paf1 complex. RNA interference (RNAi)-mediated depletion of Paf1 or Rtf1 leads to defects in induction of Hsp70 RNA, but tandem RNAi-chromatin immunoprecipitation assays show that loss of neither Paf1 nor Rtf1 alters the density or distribution of phosphorylated Pol II on the active Hsp70 gene. However, depletion of Paf1 reduces trimethylation of histone H3 at lysine 4 in the Hsp70 promoter region and significantly decreases the recruitment of chromatin-associated factors Spt6 and FACT, suggesting that Paf1 may manifest its effects on transcription through modulating chromatin structure.

Repair of palatal defect with nasal septal flap.

Postoperative oronasal fistula in cleft palate repair is common and usually repaired with local flaps or buccal flaps with some benefits. Considering the high recurrence rate after surgery, a new method for oronasal repair using septal flaps is described.

Comparison of different approaches to the reduction of anterior temporomandibular joint dislocation: a randomized clinical trial.

This randomized clinical trial was designed to compare three different reduction methods for anterior temporomandibular joint (TMJ) dislocation. The three methods evaluated were the conventional method, wrist pivot method, and extraoral method. The study sample comprised 90 consecutive patients suffering from anterior dislocation of the TMJ, who were allocated randomly to one of the three groups. This study found success rates of 86.7% for the conventional method, 96.7% for the wrist pivot method, and 66.7% for the extraoral method. The extraoral method was more difficult for the physician and the patient than the other two methods. For the patients, the wrist pivot method was easier than the other methods. For the doctors, the extraoral method was significantly more difficult than the other methods. In conclusion, due to the absence of a biting risk with the extraoral method and the lack of a significant difference in success between this method and the conventional method, the extraoral method could be considered the appropriate first-line treatment where there is a risk of the patient biting the surgeon's hand. Given the overall benefits of the wrist pivot method, this method could be considered the first-line and gold standard treatment modality in other cases.

Palatal perforations: past and present. Two case reports and a literature review.

Syphilis and cocaine abuse are posing a growing public health problem on a global and national scale. Clinicians are increasingly likely to come across associated oral manifestations. We present two cases of palatal perforations caused by tertiary syphilis and cocaine abuse respectively. The literature review discusses issues specific to palatal perforations and those general to both conditions. The purpose of the report is to focus attention on syphilis and cocaine abuse as rising problems for the dental profession.

Relative incidence of spinal canal tumors.

By a retrospective study, the relative incidence of various histopathological types of one hundred and seventy-nine biopsy proven tumors of the spinal canal from a general hospital in Iran is presented and compared with the statistics reported from several eastern countries and the west. Nerve sheath cell tumors are more frequent in the east especially in far eastern countries whereas meningiomas and neuroepithelial tumors have a lower percentage in most eastern reports. With the available data no conclusion can be drawn as to the geographic difference in the frequency of occurrence of other histopathological types appearing in the spinal canal; some statistical features in this latter group are pointed out.

Use of nasal packs and intranasal septal splints following septoplasty.

The aim of this study was to compare the efficacy of a trans-septum suturing technique with conventional nasal packing and intranasal splints in the classic septoplasty operation. The study is a prospective, randomized clinical trial. 114 patients underwent septoplasty for septal deviation and ensuing nasal obstruction. These patients were divided into two groups: packing (using intranasal septal splints and antibiotic meshes at the end of the operation) and non-packing (using four separate trans-septum through and through horizontal mattress sutures without any mesh or intranasal splint insertion). Randomization was performed using the four block randomization system. Patients who failed the regular follow-up were excluded, and the two groups were compared for postoperative bleeding, hematoma, perforation and synechiae. Patients were asked to record pain levels using a visual analogue scale. The authors found no significant statistical differences between the two groups in the parameters studied, but significantly higher pain levels were noted in the patients in the packing group. The final results confirmed that patients who underwent septoplasty, intranasal packing and septal splint insertion did not benefit more than those who had trans-septum through and through suturing.

Transient facial nerve baroparesis: case report.

We present a rare case of facial paralysis that was unusual not only in its causation but also in its rapidity of onset and recovery. We describe a rare case history of this accruing in 35 years old women traveling at the high altitude mountain road referred to ENT clinic with sudden symptoms of middle ear effusion and facial nerve paralysis. Patient had undergone medical systemic steroid treatment and after 3-4 weeks she had a good recovery of facial palsy with a minimum remnant of sensory neural hearing loss. Facial nerve paralysis resulting from a barotrauma of the middle ear is suggested. The correct diagnosis of this condition is important and unnecessary treatment should be avoided.

Intranuclear distribution and local dynamics of RNA polymerase II during transcription activation.

Transcription activation causes dramatic changes in a gene's compaction and macromolecular associations and, in some cases, triggers the translocation of the gene to a nuclear substructure. Here, we evaluate the location, movement, and transcriptional dynamics of Drosophila heat shock (HS) genes both by two-photon microscopy in live polytene nuclei and by FISH in diploid nuclei. The different HS loci occupy separate nuclear positions. Although these loci decondense upon HS, they do not undergo a detectable net translocation nor are they preferentially localized to the nuclear periphery or interior. Additionally, fluorescence recovery after photobleaching reveals that, shortly after HS, newly recruited RNA polymerase II (Pol II) enters elongation via an "efficient entry" mode, which is followed by the progressive establishment of transcription "compartments" at Hsp70 loci where concentrated Pol II is used in a "local recycling" mode. Pol II at highly transcribed developmental loci exhibits dynamics resembling combinations of these Hsp70 transcription modes.