ABSTRACT Transposable elements (TEs) threaten genomic integrity, yet their pervasive presence indicates the limitations of existing silencing mechanisms. A recent paper in Nature (Zhao et al. 2025) discovered the SOS splicing system, which provides an RNA-level defense that excises DNA transposons from mRNAs, thereby restoring gene sequence. This spliceosome-independent pathway, mediated by AKAP17A, CAAP1, and RTCB, recognizes dsRNA hairpins formed by inverted terminal repeats (ITRs) and religates the resulting RNA fragments. From an evolutionary perspective, SOS splicing exemplifies a post-transcriptional error-correction mechanism that mitigates the deleterious consequence of TE insertions, paralleling the Constructive Neutral Evolution (CNE) framework. In contrast, ADAR-mediated A-to-I RNA editing suppresses the MDA5-triggered innate immune responses to TE-derived dsRNAs, effectively tolerating rather than eliminating TEs. There may be partial overlap between ADAR and SOS substrates. ADAR editing may delay but not prevent SOS splicing, while SOS excision removes ADAR substrates. The lethality of ADAR loss underscores its role as the mechanism mitigating purifying selection on TEs and thus may contribute to their genomic tolerance and proliferation. Collectively, while ADAR masks the harm of TEs, SOS splicing actively repairs the resulting damage, together illustrating a delicate evolutionary balance between TE tolerance and transcriptomic rescue.

ABSTRACT Human Immunodeficiency Virus 1 (HIV-1) is the causative agent for acquired immunodeficiency syndrome (AIDS). Antiretroviral therapy has turned HIV-1 from a lethal disease to a chronic condition but is not curative due to the persistence of a small reservoir of latently infected cells. The molecular mechanisms driving HIV-1 latency have been extensively studied, thus far largely focusing on transcriptional regulation. Here, we summarize well established and newly discovered mechanisms of HIV-1 latency, as well as how studies of the HIV-1 promoter have informed the broader transcription field. As a strategy toward HIV-1 cure, latency reversal agents (LRAs) have been developed to pharmacologically target blocks in HIV-1 transcription to achieve reactivation of viral gene expression. However, clinical studies indicate that LRAs have largely failed to sufficiently activate the reservoir such that viral protein is produced, and there was no reduction in the size of the viral reservoir. Indeed it has become clear that co- and post-transcriptional mechanisms are also at play to regulate HIV-1 gene expression and may also serve as attractive targetable blocks. We also outline recent developments in technologies allowing the ex vivo characterization of the HIV-1 reservoir in people living with HIV (PWH). These novel technologies enable us to interrogate the different molecular compartments such as integrated intact and defective proviral HIV-1 DNA, unspliced and spliced RNA, and protein levels that provide unprecedented new insight into latency mechanisms. Lastly, the potential of different transcription-targeting cure strategies is discussed in light of the contributions of co- and posttranscriptional blocks and the advent of Long Acting (LA)-ART.

ABSTRACT RNA polymerases are the central enzymes of gene expression and function frequently in either a head-on or co-directional manner on the busy DNA track. Whether and how these collisions between RNA polymerases contribute to transcriptional regulation is mysterious. Increasing evidence from biochemical and single-molecule studies suggests that RNA polymerase collisions function as an important regulator to fine-tune transcription, rather than creating deleterious “traffic jams”. This review summarizes the recent progress on elucidating the consequences of RNA polymerase collisions during transcription and highlights the significance of cooperation and coordination between RNA polymerases.

ABSTRACT The rising threat of antibiotic resistance in pathogenic bacteria emphasizes the need for new therapeutic strategies. This review focuses on bacterial transcription factors (TFs), which play crucial roles in bacterial pathogenesis. We discuss the regulatory roles of these factors through examples, and we outline potential therapeutic strategies targeting bacterial TFs. Specifically, we discuss the use of small molecules to interfere with TF function and the development of transcription factor decoys, oligonucleotides that compete with promoters for TF binding. We also cover peptides that target the interaction between the bacterial TF and other factors, such as RNA polymerase, and the targeting of sigma factors. These strategies, while promising, come with challenges, from identifying targets to designing interventions, managing side effects, and accounting for changing bacterial resistance patterns. We also delve into how Artificial Intelligence contributes to these efforts and how it may be exploited in the future, and we touch on the roles of multidisciplinary collaboration and policy to advance this research domain. Abbreviations: AI, artificial intelligence; CNN, convolutional neural networks; DTI: drug-target interaction; HTH, helix-turn-helix; IHF, integration host factor; LTTRs, LysR-type transcriptional regulators; MarR, multiple antibiotic resistance regulator; MRSA, methicillin resistant Staphylococcus aureus; MSA: multiple sequence alignment; NAP, nucleoid-associated protein; PROTACs, proteolysis targeting chimeras; RNAP, RNA polymerase; TF, transcription factor; TFD, transcription factor decoying; TFTRs, TetR-family transcriptional regulators; wHTH, winged helix-turn-helix.

ABSTRACT The profiling of gene expression patterns to glean biological insights from single cells has become commonplace over the last few years. However, this approach overlooks the transcript contents that can differ between individual cells and cell populations. In this review, we describe early work in the field of single-cell short-read sequencing as well as full-length isoforms from single cells. We then describe recent work in single-cell long-read sequencing wherein some transcript elements have been observed to work in tandem. Based on earlier work in bulk tissue, we motivate the study of combination patterns of other RNA variables. Given that we are still blind to some aspects of isoform biology, we suggest possible future avenues such as CRISPR screens which can further illuminate the function of RNA variables in distinct cell populations.

ABSTRACT Proximity ligation assay (PLA) is an immunofluorescence assay, which determines in situ interaction of two biomolecules present within 40 nm close proximity. Here, we describe a modification of PLA for visual detection of in situ protein interactions with nascent RNA in a single cell (IPNR-PLA). In IPNR-PLA, nascent RNA is labeled by incorporating 5-fluorouridine (FU), a uridine nucleotide analogue, followed by covalent cross-linking of the interacting partners in proximity to newly synthesized RNA. By using combination of anti-BrdU antibody, which specifically binds to FU, and primary antibody against a protein of interest, the IPNR reaction results in fluorescent puncta as a positive signal, only if the candidate proteins are in proximity to nascent RNA. We have validated this method by demonstrating known CDK9 and elongating RNA pol II interaction with nascent RNA. Finally, we used this method to test for the presence of DNA double strand breaks as well as Poly (ADP-ribose) polymerase 1 (PARP1), an RNA binding protein, in the vicinity of nascent RNA in cancer cells. The capability of performing parallel IF labeling and quantifiable multiparameter measurements within heterogeneous cell populations makes IPNR-PLA very attractive for use in biological studies. Overall, we have developed the IPNR-PLA method for analysis of protein association with nascent RNA with single-cell resolution, which is highly sensitive, quantitative, efficient, and requires little starting experimental material.

ABSTRACT The Integrator was originally discovered as a specialized 3’-end processing endonuclease complex required for maturation of RNA polymerase II (RNAPII)-dependent small nuclear RNAs (snRNAs). Since its discovery, Integrator’s spectrum of substrates was significantly expanded to include non-polyadenylated long noncoding RNAs (lncRNA), enhancer RNAs (eRNAs), telomerase RNA (tertRNA), several Herpesvirus transcripts, and messenger RNAs (mRNAs). Recently emerging transcriptome-wide studies reveled an important role of the Integrator in protein-coding genes, where it contributes to gene expression regulation through promoter-proximal transcription attenuation. These new functional data are complemented by several structures of Integrator modules and higher-order complexes, providing mechanistic insights into Integrator-mediated processing events. In this work, we summarize recent progress in our understanding of the structure and function of the Integrator complex.

ABSTRACT Chromatin accessibility is generally perceived as a common property of active regulatory elements where transcription factors are recruited via DNA-specific interactions and other physico-chemical properties to regulate gene transcription. Recent work in the context of mitosis provides less trivial and potentially more interesting relationships than previously anticipated.