LARP7 suppresses P-TEFb activity to inhibit breast cancer progression and metastasis.

Transcriptional elongation by RNA polymerase (Pol) II is essential for gene expression during cell growth and differentiation. The positive transcription elongation factor b (P-TEFb) stimulates transcriptional elongation by phosphorylating Pol II and antagonizing negative elongation factors. A reservoir of P-TEFb is sequestered in the inactive 7SK snRNP where 7SK snRNA and the La-related protein LARP7 are required for the integrity of this complex. Here, we show that P-TEFb activity is important for the epithelial-mesenchymal transition (EMT) and breast cancer progression. Decreased levels of LARP7 and 7SK snRNA redistribute P-TEFb to the transcriptionally active super elongation complex, resulting in P-TEFb activation and increased transcription of EMT transcription factors, including Slug, FOXC2, ZEB2, and Twist1, to promote breast cancer EMT, invasion, and metastasis. Our data provide the first demonstration that the transcription elongation machinery plays a key role in promoting breast cancer progression by directly controlling the expression of upstream EMT regulators

Viral-Host Interactions That Control HIV-1 Transcriptional Elongation

本综述论文针对艾滋病病毒HIV转录研究的最新进展，对各种P-TEFb复合体的结构、功能、及其与艾滋病病毒HIV编码的Tat蛋白的相互作用、Tat的翻译后修饰、以及艾滋病病毒HIV的转录调控机制进行了综述，提高了对艾滋病病毒转录延伸机制的理解，创新性地提出了对抗艾滋病病毒感染及潜伏的新策略，在理论研究及应用方面意义重大。Regulation of the pause and elongation by ribonucleic acid (RNA) polymerase II (Pol II) is used widely by metazoans to attain the pattern of gene expression that is essential for optimal cell growth/renewal, differentiation, and stress response. Currently, much of what we know about Pol II elongation control comes from pioneering studies of the HIV-1-encoded transactivating (Tat) protein and its host cellular cofactors. The interaction between the two fuels a powerful feedback circuit that activates human immunodeficiency virus (HIV) transcription and prevents the virus from entering latency. One of the key Tat cofactors is the human positive transcription elongation factor b (P-TEFb), which exists in a family of complexes with distinct functions during Tat transactivation. This article reviews recent progress in HIV transcription research with an emphasis on the intricate control of the various P-TEFb complexes, structural and functional insights into their interactions with Tat, the multifaceted roles of posttranslational modifications of Tat, and epigenetic control of HIV chromatin in modulating Tat activity and HIV latency. The knowledge from these studies will not only help the design of better strategies to fight HIV infection and transcriptional latency, but also advance the overall understanding of the mechanism controlling transcriptional elongation in general.http://news.xmu.edu.cn/s/13/t/542/22/6b/info139883.ht

The two-component system CpxAR is required for the high potassium stress survival of Actinobacillus pleuropneumoniae

IntroductionActinobacillus pleuropneumoniae is an important respiratory pathogen, which can cause porcine contagious pleuropneumonia and lead to great economic losses to worldwide swine industry. High potassium is an adverse environment for bacteria, which is not conducive to providing turgor pressure for cell growth and division. Two-component system CpxAR is an important regulatory system of bacteria in response to environmental changes, which is involved in a variety of biological activities, such as antibiotic resistance, periplasmic protein folding, peptidoglycan metabolism and so on.MethodsHowever, little is known about the role of CpxAR in high potassium stress in A. pleuropneumoniae. Here, we showed that CpxAR is critical for cell division of A. pleuropneumoniae under high potassium (K+) stress.ResultsqRT-PCR analysis found that CpxAR positively regulated the cell division genes ftsEX. In addition, we also demonstrated that CpxR-P could directly bind the promoter region of the cell division gene ftsE by EMSA.DiscussionIn conclusion, our results described a mechanism where CpxAR adjusts A. pleuropneumoniae survival under high-K+ stress by upregulating the expression of the cell division proteins FtsE and FtsX. These findings are the first to directly demonstrate CpxAR-mediated high-K+ tolerance, and to investigate the detailed molecular mechanism

Autoinflammatory mutation in NLRC4 reveals a leucine-rich repeat (LRR)-LRR oligomerization interface

Background Monogenic autoinflammatory disorders are characterized by dysregulation of the innate immune system, for example by gain-of-function mutations in inflammasome-forming proteins, such as NOD-like receptor family CARD-containing 4 protein (NLRC4). Objective Here we investigate the mechanism by which a novel mutation in the leucine-rich repeat (LRR) domain of NLRC4 (c.G1965C, p.W655C) contributes to autoinflammatory disease. Methods: We studied 2 unrelated patients with early-onset macrophage activation syndrome harboring the same de novo mutation in NLRC4. In vitro inflammasome complex formation was quantified by using flow cytometric analysis of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 techniques and lentiviral transduction were used to generate THP-1 cells with either wild-type or mutant NLRC4 cDNA. Cell death and release of IL-1β/IL-18 were quantified by using flow cytometry and ELISA, respectively. Results The p.W655C NLRC4 mutation caused increased ASC speck formation, caspase-1–dependent cell death, and IL-1β/IL-18 production. ASC contributed to p.W655C NLRC4–mediated cytokine release but not cell death. Mutation of p.W655 activated the NLRC4 inflammasome complex by engaging with 2 interfaces on the opposing LRR domain of the oligomer. One key set of residues (p.D1010, p.D1011, p.L1012, and p.I1015) participated in LRR-LRR oligomerization when triggered by mutant NLRC4 or type 3 secretion system effector (PrgI) stimulation of the NLRC4 inflammasome complex. Conclusion This is the first report of a mutation in the LRR domain of NLRC4 causing autoinflammatory disease. c.G1965C/p.W655C NLRC4 increased inflammasome activation in vitro. Data generated from various NLRC4 mutations provides evidence that the LRR-LRR interface has an important and previously unrecognized role in oligomerization of the NLRC4 inflammasome complex

A Minor Subset of Super Elongation Complexes Plays a Predominant Role in Reversing HIV-1 Latency

Promoter-proximal pausing by RNA polymerase II (Pol II) is a key rate-limiting step in HIV-1 transcription and latency reversal. The viral Tat protein recruits human super elongation complexes (SECs) to paused Pol II to overcome this restriction. Despite the recent progress in understanding the functions of different subsets of SECs in controlling cellular and Tat-activated HIV transcription, little is known about the SEC subtypes that help reverse viral latency in CD4(+) T cells. Here, we used the CRISPR-Cas9 genome-editing tool to knock out the gene encoding the SEC subunit ELL2, AFF1, or AFF4 in Jurkat/2D10 cells, a well-characterized HIV-1 latency model. Depletion of these proteins drastically reduced spontaneous and drug-induced latency reversal by suppressing HIV-1 transcriptional elongation. Surprisingly, a low-abundance subset of SECs containing ELL2 and AFF1 was found to play a predominant role in cooperating with Tat to reverse latency. By increasing the cellular level/activity of these Tat-friendly SECs, we could potently activate latent HIV-1 without using any drugs. These results implicate the ELL2/AFF1-SECs as an important target in the future design of a combinatorial therapeutic approach to purge latent HIV-1

A Minor Subset of Super Elongation Complexes Plays a Predominant Role in Reversing HIV-1 Latency

Promoter-proximal pausing by RNA polymerase II (Pol II) is a key rate-limiting step in HIV-1 transcription and latency reversal. The viral Tat protein recruits human super elongation complexes (SECs) to paused Pol II to overcome this restriction. Despite the recent progress in understanding the functions of different subsets of SECs in controlling cellular and Tat-activated HIV transcription, little is known about the SEC subtypes that help reverse viral latency in CD4(+) T cells. Here, we used the CRISPR-Cas9 genome-editing tool to knock out the gene encoding the SEC subunit ELL2, AFF1, or AFF4 in Jurkat/2D10 cells, a well-characterized HIV-1 latency model. Depletion of these proteins drastically reduced spontaneous and drug-induced latency reversal by suppressing HIV-1 transcriptional elongation. Surprisingly, a low-abundance subset of SECs containing ELL2 and AFF1 was found to play a predominant role in cooperating with Tat to reverse latency. By increasing the cellular level/activity of these Tat-friendly SECs, we could potently activate latent HIV-1 without using any drugs. These results implicate the ELL2/AFF1-SECs as an important target in the future design of a combinatorial therapeutic approach to purge latent HIV-1

LARP7 suppresses P-TEFb activity to inhibit breast cancer progression and metastasis.

Transcriptional elongation by RNA polymerase (Pol) II is essential for gene expression during cell growth and differentiation. The positive transcription elongation factor b (P-TEFb) stimulates transcriptional elongation by phosphorylating Pol II and antagonizing negative elongation factors. A reservoir of P-TEFb is sequestered in the inactive 7SK snRNP where 7SK snRNA and the La-related protein LARP7 are required for the integrity of this complex. Here, we show that P-TEFb activity is important for the epithelial-mesenchymal transition (EMT) and breast cancer progression. Decreased levels of LARP7 and 7SK snRNA redistribute P-TEFb to the transcriptionally active super elongation complex, resulting in P-TEFb activation and increased transcription of EMT transcription factors, including Slug, FOXC2, ZEB2, and Twist1, to promote breast cancer EMT, invasion, and metastasis. Our data provide the first demonstration that the transcription elongation machinery plays a key role in promoting breast cancer progression by directly controlling the expression of upstream EMT regulators

Phase separation in gene transcription control

Phase separation provides a general mechanism for the formation of biomolecular condensates, and it plays a vital role in regulating diverse cellular processes, including gene expression. Although the role of transcription factors and coactivators in regulating transcription has long been understood, how phase separation is involved in this process is just beginning to be explored. In this review, we highlight recent advance in elucidating the molecular mechanisms and functions of transcriptional condensates in gene expression control. We discuss the different condensates formed at each stage of the transcription cycle and how they are dynamically regulated in response to diverse cellular and extracellular cues that cause rapid changes in gene expression. Furthermore, we present new findings regarding the dysregulation of transcription condensates and their implications in human diseases