Promoter-proximal Pausing Of RNA Polymerase Research Articles

Evolution of promoter-proximal pausing enabled a new layer of transcription control.

Promoter-proximal pausing of RNA polymerase II (Pol II) is a key regulatory step during transcription. Despite the central role of pausing in gene regulation, we do not understand the evolutionary processes that led to the emergence of Pol II pausing or its transition to a rate-limiting step actively controlled by transcription factors. Here we analyzed transcription in species across the tree of life. Unicellular eukaryotes display a slow acceleration of Pol II near transcription start sites that transitioned to a longer-lived, focused pause in metazoans. This event coincided with the evolution of new subunits in the NELF and 7SK complexes. Depletion of NELF in mammals shifted the promoter-proximal buildup of Pol II from the pause site into the early gene body and compromised transcriptional activation for a set of heat shock genes. Our work details the evolutionary history of Pol II pausing and sheds light on how new transcriptional regulatory mechanisms evolve.

ARGLU1 enhances promoter-proximal pausing of RNA polymerase II and stimulates DNA damage repair.

Arginine and glutamate rich 1 (ARGLU1) is a poorly understood cellular protein with functions in RNA splicing and transcription. Computational prediction suggests that ARGLU1 contains intrinsically disordered regions and lacks any known structural or functional domains. We used adenovirus Early protein 1A (E1A) to probe for critical regulators of important cellular pathways and identified ARGLU1 as a significant player in transcription and the DNA damage response pathway. Transcriptional effects induced by ARGLU1 occur via enhancement of promoter-proximal RNA polymerase II pausing, likely by inhibiting the interaction between JMJD6 and BRD4. When overexpressed, ARGLU1 increases the growth rate of cancer cells, while its knockdown leads to growth arrest. Significantly, overexpression of ARGLU1 increased cancer cell resistance to genotoxic drugs and promoted DNA damage repair. These results identify new roles for ARGLU1 in cancer cell survival and the DNA damage repair pathway, with potential clinical implications for chemotherapy resistance.

RNA polymerase II pausing temporally coordinates cell cycle progression and erythroid differentiation.

Controlled release of promoter-proximal paused RNA polymerase II (RNA Pol II) is crucial for gene regulation. However, studying RNA Pol II pausing is challenging, as pause-release factors are almost all essential. In this study, we identified heterozygous loss-of-function mutations in SUPT5H, which encodes SPT5, in individuals with β-thalassemia. During erythropoiesis in healthy human cells, cell cycle genes were highly paused as cells transition from progenitors to precursors. When the pathogenic mutations were recapitulated by SUPT5H editing, RNA Pol II pause release was globally disrupted, and as cells began transitioning from progenitors to precursors, differentiation was delayed, accompanied by a transient lag in erythroid-specific gene expression and cell cycle kinetics. Despite this delay, cells terminally differentiate, and cell cycle phase distributions normalize. Therefore, hindering pause release perturbs proliferation and differentiation dynamics at a key transition during erythropoiesis, identifying a role for RNA Pol II pausing in temporally coordinating the cell cycle and erythroid differentiation.

INTAC endonuclease and phosphatase modules differentially regulate transcription by RNA polymerase II

Gene expression in metazoans is controlled by promoter-proximal pausing of RNA polymerase II, which can undergo productive elongation or promoter-proximal termination. Integrator-PP2A (INTAC) plays a crucial role in determining the fate of paused polymerases, but the underlying mechanisms remain unclear. Here, we establish a rapid degradation system to dissect the functions of INTAC RNA endonuclease and phosphatase modules. We find that both catalytic modules function at most if not all active promoters and enhancers, yet differentially affect polymerase fate. The endonuclease module induces promoter-proximal termination, with its disruption leading to accumulation of elongation-incompetent polymerases and downregulation of highly expressed genes, while elongation-competent polymerases accumulate at lowly expressed genes and non-coding elements, leading to their upregulation. The phosphatase module primarily prevents the release of paused polymerases and limits transcriptional activation, especially for highly paused genes. Thus, both INTAC catalytic modules have unexpectedly general yet distinct roles in dynamic transcriptional control.

ERK-mediated NELF-A phosphorylation promotes transcription elongation of immediate-early genes by releasing promoter-proximal pausing of RNA polymerase II

Growth factor-induced, ERK-mediated induction of immediate-early genes (IEGs) is crucial for cell growth and tumorigenesis. Although IEG expression is mainly regulated at the level of transcription elongation by RNA polymerase-II (Pol-II) promoter-proximal pausing and its release, the role of ERK in this process remains unknown. Here, we identified negative elongation factor (NELF)-A as an ERK substrate. Upon growth factor stimulation, ERK phosphorylates NELF-A, which dissociates NELF from paused Pol-II at the promoter-proximal regions of IEGs, allowing Pol-II to resume elongation and produce full-length transcripts. Furthermore, we found that in cancer cells, PP2A efficiently dephosphorylates NELF-A, thereby preventing aberrant IEG expression induced by ERK-activating oncogenes. However, when PP2A inhibitor proteins are overexpressed, as is frequently observed in cancers, decreased PP2A activity combined with oncogene-mediated ERK activation conspire to induce NELF-A phosphorylation and IEG upregulation, resulting in tumor progression. Our data delineate previously unexplored roles of ERK and PP2A inhibitor proteins in carcinogenesis.

SETD5 modulates homeostasis of hematopoietic stem cells by mediating RNA Polymerase II pausing in cooperation with HCF-1

SETD5 mutations were identified as the genetic causes of neurodevelopmental disorders. While the whole-body knockout of Setd5 in mice leads to embryonic lethality, the role of SETD5 in adult stem cell remains unexplored. Here, a critical role of Setd5 in hematopoietic stem cells (HSCs) is identified. Specific deletion of Setd5 in hematopoietic system significantly increased the number of immunophenotypic HSCs by promoting HSC proliferation. Setd5-deficient HSCs exhibited impaired long-term self-renewal capacity and multiple-lineage differentiation potentials under transplantation pressure. Transcriptome analysis of Setd5-deficient HSCs revealed a disruption of quiescence state of long-term HSCs, a cause of the exhaustion of functional HSCs. Mechanistically, SETD5 was shown to regulate HSC quiescence by mediating the release of promoter-proximal paused RNA polymerase II (Pol II) on E2F targets in cooperation with HCF-1 and PAF1 complex. Taken together, these findings reveal an essential role of SETD5 in regulating Pol II pausing-mediated maintenance of adult stem cells.

STL-seq reveals pause-release and termination kinetics for promoter-proximal paused RNA polymerase II transcripts

Despite the critical regulatory function of promoter-proximal pausing, the influence of pausing kinetics on transcriptional control remains an active area of investigation. Here, we present Start-TimeLapse-seq (STL-seq), a method that captures the genome-wide kinetics of short, capped RNA turnover and reveals principles of regulation at the pause site. By measuring the rates of release into elongation and premature termination through the inhibition of pause release, we determine that pause-release rates are highly variable, and most promoter-proximal paused RNA polymerase II molecules prematurely terminate (∼80%). The preferred regulatory mechanism upon a hormonal stimulus (20-hydroxyecdysone) is to influence pause-release rather than termination rates. Transcriptional shutdown occurs concurrently with the induction of promoter-proximal termination under hyperosmotic stress, but paused transcripts from TATA box-containing promoters remain stable, demonstrating an important role for cis-acting DNA elements in pausing. STL-seq dissects the kinetics of pause release and termination, providing an opportunity to identify mechanisms of transcriptional regulation.

Stochastic pausing at latent HIV-1 promoters generates transcriptional bursting

Promoter-proximal pausing of RNA polymerase II is a key process regulating gene expression. In latent HIV-1 cells, it prevents viral transcription and is essential for latency maintenance, while in acutely infected cells the viral factor Tat releases paused polymerase to induce viral expression. Pausing is fundamental for HIV-1, but how it contributes to bursting and stochastic viral reactivation is unclear. Here, we performed single molecule imaging of HIV-1 transcription. We developed a quantitative analysis method that manages multiple time scales from seconds to days and that rapidly fits many models of promoter dynamics. We found that RNA polymerases enter a long-lived pause at latent HIV-1 promoters (>20 minutes), thereby effectively limiting viral transcription. Surprisingly and in contrast to current models, pausing appears stochastic and not obligatory, with only a small fraction of the polymerases undergoing long-lived pausing in absence of Tat. One consequence of stochastic pausing is that HIV-1 transcription occurs in bursts in latent cells, thereby facilitating latency exit and providing a rationale for the stochasticity of viral rebounds.

The CDK7 Inhibitor THZ1 Alters RNA Polymerase Dynamics at the 5‘ and 3‘ Ends of Genes

The t(8;21) is one of the most frequent chromosomal translocations in acute myeloid leukemia (AML). This translocation encodes a fusion protein containing the DNA binding domain of RUNX1, a master regulator of hematopoiesis, linked to the majority of the myeloid translocation gene on chromosome 8 (MTG8, also known as eight-twenty-one or ETO; gene name RUNX1T1). This chimeric fusion protein binds to the RUNX1 DNA elements to control gene expression by recruiting transcriptional cofactors via the MTG8/ETO moiety. In addition, MTG/ETO family proteins co-purified in a complex that also contained “E proteins” and the cyclin dependent kinase CDK9, a component of the positive transcription elongation factor b (P-TEFb).P-TEFb contains Cyclin T1 and CDK9 and several potential CDK9 inhibitors have shown promise in the clinics for t(8;21) AML, such as flavopiridol (alvocidib). Transcription initiation, promoter-proximal pausing of RNA polymerase II (RNAPII), and transcription elongation are events that are highly regulated for genes involved in proliferation and differentiation such as MYC and BCL2 . CDK7 phosphorylates Ser5 of the C-terminal domain of RNAPII to trigger promoter-proximal pausing of RNA polymerase II, whereas CDK9 phosphorylates Ser2 of RNAPII and the negative elongation factors DSIF and NELF to release the polymerase into the body of the gene.In this study, we used inhibitors of CDK7 and CDK9 to probe for transcriptional vulnerabilities in t(8;21) AML. We used both broad spectrum (flavopiridol, dinacicilib) and a specific CDK9 inhibitor PHA767491 along with THZ1 (CDK7 inhibitor). Since CDK7 is also a CAK (CDK activating kinase) that activates cell-cycle CDKs and mutations in Cyclin D2 are common in t(8;21) AML, we also tested the highly selective CDK4/6 inhibitor palbociclib (PD-0332991). We observed that the t(8;21)-containing AML cell lines SKNO-1 and Kasumi-1, as well as primary AML patient cells, were extremely sensitive to all the CDK7/9 inhibitors, but not palbociclib. We used precision global run-on transcription sequencing (PROseq) to define the mechanism of action of these compounds. This technique creates high resolution genomic maps of the active RNA polymerases to define the effects on RNA polymerase dynamics. CDK9 inhibitors caused wide spread RNA Polymerase II promoter proximal pausing at nearly 80% of the expressed genes, as well as at enhancers where there was a general impairment of production of eRNAs and lncRNAs. Conversely, inhibition of CDK7, a critical component of TFIIH caused a loss of paused RNA polymerase II at promoters, which was associated with an increase of polymerases in the body of genes. While RUNX1 was reported to be regulated by CDK7 in T-ALL, there was no impact on the expression of RUNX1 or the fusion protein in t(8;21)-containing cells. Although enhancers were not affected, super enhancers were modestly affected by THZ1. Interestingly, within a subset of genes that showed increased RNA polymerase accumulation within the gene body, CDK7 inhibition altered 3' end transcription termination dynamics within 1 hr and this effect remained even at 2 hr. A time course of THZ1 treatment at 0, 15', 30', and 60' suggested that CDK7 inhibition altered RNA polymerase dynamics at 5'ends of the genes, and it's these effects that eventually affected transcription termination at the 3' ends of the genes. DisclosuresSavona:Amgen: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; Takeda: Research Funding; Karyopharm: Consultancy, Equity Ownership; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Consultancy, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.

DDB1 binds histone reader BRWD3 to activate the transcriptional cascade in adipogenesis and promote onset of obesity.

Obesity has become a global pandemic. Identification of key factors in adipogenesis helps to tackle obesity and related metabolic diseases. Here, we show that DDB1 binds the histone reader BRWD3 to promote adipogenesis and diet-induced obesity. Although typically recognized as a component of the CUL4-RING E3 ubiquitin ligase complex, DDB1 stimulates adipogenesis independently of CUL4. A DDB1 mutant that does not bind CUL4A or CUL4B fully restores adipogenesis in DDB1-deficient cells. Ddb1+/- mice show delayed postnatal development of white adipose tissues and are protected from diet-induced obesity. Mechanistically, by interacting with BRWD3, DDB1 is recruited to acetylated histones in the proximal promoters of ELK1 downstream immediate early response genes and facilitates the release of paused RNA polymerase II, thereby activating the transcriptional cascade in adipogenesis. Our findings have uncovered a CUL4-independent function of DDB1 in promoting the transcriptional cascade of adipogenesis, development of adipose tissues, and onset of obesity.

Pausing sites of RNA polymerase II on actively transcribed genes are enriched in DNA double-stranded breaks

DNA double-stranded breaks (DSBs) are strongly associated with active transcription, and promoter-proximal pausing of RNA polymerase II (Pol II) is a critical step in transcriptional regulation. Mapping the distribution of DSBs along actively expressed genes and identifying the location of DSBs relative to pausing sites can provide mechanistic insights into transcriptional regulation. Using genome-wide DNA break mapping/sequencing techniques at single-nucleotide resolution in human cells, we found that DSBs are preferentially located around transcription start sites of highly transcribed and paused genes and that Pol II promoter-proximal pausing sites are enriched in DSBs. We observed that DSB frequency at pausing sites increases as the strength of pausing increases, regardless of whether the pausing sites are near or far from annotated transcription start sites. Inhibition of topoisomerase I and II by camptothecin and etoposide treatment, respectively, increased DSBs at the pausing sites as the concentrations of drugs increased, demonstrating the involvement of topoisomerases in DSB generation at the pausing sites. DNA breaks generated by topoisomerases are short-lived because of the religation activity of these enzymes, which these drugs inhibit; therefore, the observation of increased DSBs with increasing drug doses at pausing sites indicated active recruitment of topoisomerases to these sites. Furthermore, the enrichment and locations of DSBs at pausing sites were shared among different cell types, suggesting that Pol II promoter-proximal pausing is a common regulatory mechanism. Our findings support a model in which topoisomerases participate in Pol II promoter-proximal pausing and indicated that DSBs at pausing sites contribute to transcriptional activation.

JMJD6 cleaves MePCE to release positive transcription elongation factor b (P-TEFb) in higher eukaryotes.

More than 30% of genes in higher eukaryotes are regulated by promoter-proximal pausing of RNA polymerase II (Pol II). Phosphorylation of Pol II CTD by positive transcription elongation factor b (P-TEFb) is a necessary precursor event that enables productive transcription elongation. The exact mechanism on how the sequestered P-TEFb is released from the 7SK snRNP complex and recruited to Pol II CTD remains unknown. In this report, we utilize mouse and human models to reveal methylphosphate capping enzyme (MePCE), a core component of the 7SK snRNP complex, as the cognate substrate for Jumonji domain-containing 6 (JMJD6)'s novel proteolytic function. Our evidences consist of a crystal structure of JMJD6 bound to methyl-arginine, enzymatic assays of JMJD6 cleaving MePCE in vivo and in vitro, binding assays, and downstream effects of Jmjd6 knockout and overexpression on Pol II CTD phosphorylation. We propose that JMJD6 assists bromodomain containing 4 (BRD4) to recruit P-TEFb to Pol II CTD by disrupting the 7SK snRNP complex.

Analog-sensitive cell line identifies cellular substrates of CDK9.

Transcriptional cyclin-dependent kinases regulate all phases of transcription. Cyclin-dependent kinase 9 (CDK9) has been implicated in the regulation of promoter-proximal pausing of RNA polymerase II and more recently in transcription termination. Study of the substrates of CDK9 has mostly been limited to in vitro approaches that lack a quantitative assessment of CDK9 activity. Here we analyzed the cellular phosphoproteome upon inhibition of CDK9 by combining analog-sensitive kinase technology with quantitative phosphoproteomics in Raji B-cells. Our analysis revealed the activity of CDK9 on 1102 phosphosites quantitatively, and we identified 120 potential cellular substrates. Furthermore, a substantial number of CDK9 substrates were described as splicing factors, highlighting the role of CDK9 in transcription-coupled splicing events. Based on comparison to in vitro data, our findings suggest that cellular context fundamentally impacts the activity of CDK9 and specific selection of its substrates.

An improved auxin-inducible degron system preserves native protein levels and enables rapid and specific protein depletion.

Rapid perturbation of protein function permits the ability to define primary molecular responses while avoiding downstream cumulative effects of protein dysregulation. The auxin-inducible degron (AID) system was developed as a tool to achieve rapid and inducible protein degradation in nonplant systems. However, tagging proteins at their endogenous loci results in chronic auxin-independent degradation by the proteasome. To correct this deficiency, we expressed the auxin response transcription factor (ARF) in an improved inducible degron system. ARF is absent from previously engineered AID systems but is a critical component of native auxin signaling. In plants, ARF directly interacts with AID in the absence of auxin, and we found that expression of the ARF PB1 (Phox and Bem1) domain suppresses constitutive degradation of AID-tagged proteins. Moreover, the rate of auxin-induced AID degradation is substantially faster in the ARF-AID system. To test the ARF-AID system in a quantitative and sensitive manner, we measured genome-wide changes in nascent transcription after rapidly depleting the ZNF143 transcription factor. Transcriptional profiling indicates that ZNF143 activates transcription in cis and regulates promoter-proximal paused RNA polymerase density. Rapidly inducible degradation systems that preserve the target protein's native expression levels and patterns will revolutionize the study of biological systems by enabling specific and temporally defined protein dysregulation.

Promoter-proximal pausing of RNA polymerase II: a nexus of gene regulation

Precise spatio-temporal control of gene activity is essential for organismal development, growth, and survival in a changing environment. Decisive steps in gene regulation involve the pausing of RNA polymerase II (Pol II) in early elongation, and the controlled release of paused polymerase into productive RNA synthesis. Here we describe the factors that enable pausing and the events that trigger Pol II release into the gene. We also discuss open questions in the field concerning the stability of paused Pol II, nucleosomes as obstacles to elongation, and potential roles of pausing in defining the precision and dynamics of gene expression.

The CDK7 inhibitor THZ1 alters RNA polymerase dynamics at the 5' and 3' ends of genes.

The t(8;21) is one of the most frequent chromosomal translocations associated with acute myeloid leukemia (AML). We found that t(8;21) AML were extremely sensitive to THZ1, which triggered apoptosis after only 4 h. We used precision nuclear run-on transcription sequencing (PROseq) to define the global effects of THZ1 and other CDK inhibitors on RNA polymerase II dynamics. Inhibition of CDK7 using THZ1 caused wide-spread loss of promoter-proximal paused RNA polymerase. This loss of 5′ pausing was associated with accumulation of polymerases in the body of a large number of genes. However, there were modest effects on genes regulated by ‘super-enhancers’. At the 3′ ends of genes, treatment with THZ1 suppressed RNA polymerase ‘read through’ at the end of the last exon, which resembled a phenotype associated with a mutant RNA polymerase with slower elongation rates. Consistent with this hypothesis, polyA site-sequencing (PolyA-seq) did not detect differences in poly A sites after THZ1 treatment. PROseq analysis after short treatments with THZ1 suggested that these 3′ effects were due to altered CDK7 activity at the 5′ end of long genes, and were likely to be due to slower rates of elongation.

Promoter-proximal pausing mediated by the exon junction complex regulates splicing

Promoter-proximal pausing of RNA polymerase II (Pol II) is a widespread transcriptional regulatory step across metazoans. Here we find that the nuclear exon junction complex (pre-EJC) is a critical and conserved regulator of this process. Depletion of pre-EJC subunits leads to a global decrease in Pol II pausing and to premature entry into elongation. This effect occurs, at least in part, via non-canonical recruitment of pre-EJC components at promoters. Failure to recruit the pre-EJC at promoters results in increased binding of the positive transcription elongation complex (P-TEFb) and in enhanced Pol II release. Notably, restoring pausing is sufficient to rescue exon skipping and the photoreceptor differentiation defect associated with depletion of pre-EJC components in vivo. We propose that the pre-EJC serves as an early transcriptional checkpoint to prevent premature entry into elongation, ensuring proper recruitment of RNA processing components that are necessary for exon definition.

LncRNA HOXA-AS2 represses endothelium inflammation by regulating the activity of NF-κB signaling

Background and aimsEndothelium inflammation, which can lead to endothelial activation and dysfunction, is widely accepted as the major event in multiple vascular disorders. The lncRNA HOXA-AS2 was previously reported to be involved in multiple inflammation-linked cancers. However, the role of HOXA-AS2 in endothelium inflammation is poorly understood. This study aims to determine the regulatory role of HOXA-AS2 in endothelium inflammation and related vascular diseases. MethodsHigh throughput mRNA sequencing was performed to establish expression profiles after HOXA-AS2 depletion. We extracted total RNAs of human peripheral blood mononuclear cells from normal control group and experimental group with carotid artery atherosclerosis, and performed qRT-PCR to assay the correlation between HOXA-AS2 expression and inflammatory vascular diseases. ResultsInhibition of HOXA-AS2 can induce the activation of NF-κB signaling and subsequent inflammatory response. More importantly, HOXA-AS2 is inversely found to be inversely regulated by NF-κB in a negative feedback manner by helping recruit BRD4/P-TEFb complex to HOXA-AS2 promoter region, therefore facilitating release of the promoter-proximal paused RNA polymerase II and activating transcription elongation. ConclusionsWe identify HOXA-AS2 as a critical repressor of endothelium inflammation. Moreover, this study offers us a new way to balance the NF-κB signaling-driven excessive endothelium inflammation by establishing a NF-κB/HOXA-AS2 negative feedback loop. Based on these findings, we conclude that HOXA-AS2 may serve as a crucial therapeutic target for various vascular disorders which are significantly associated with endothelium inflammation.

Statistical inference of the rate of RNA polymerase II elongation by total RNA sequencing.

MotivationSequencing total RNA without poly-A selection enables us to obtain a transcriptomic profile of nascent RNAs undergoing transcription with co-transcriptional splicing. In general, the RNA-seq reads exhibit a sawtooth pattern in a gene, which is characterized by a monotonically decreasing gradient across introns in the 5’–3’ direction, and by substantially higher levels of RNA-seq reads present in exonic regions. Such patterns result from the process of underlying transcription elongation by RNA polymerase II, which traverses the DNA strand in a 5’–3’ direction as it performs a complex series of mRNA synthesis and processing. Therefore, data of sequenced total RNAs could be utilized to infer the rate of transcription elongation by solving the inverse problem.ResultsThough solving the inverse problem in total RNA-seq has the great potential, statistical methods have not yet been fully developed. We demonstrate what extent the newly developed method can be useful. The objective is to reconstruct the spatial distribution of transcription elongation rates in a gene from a given noisy, sawtooth-like profile. It is necessary to recover the signal source of the elongation rates separately from several types of nuisance factors, such as unobserved modes of co-transcriptionally occurring mRNA splicing, which exert significant influences on the sawtooth shape. The present method was tested using published total RNA-seq data derived from mouse embryonic stem cells. We investigated the spatial characteristics of the estimated elongation rates, focusing especially on the relation to promoter-proximal pausing of RNA polymerase II, nucleosome occupancy and histone modification patterns.Availability and implementationA C implementation of PolSter and sample data are available at https://github.com/yoshida-lab/PolSter.Supplementary information Supplementary data are available at Bioinformatics online.

Cyclin D1 overexpression induces global transcriptional downregulation in lymphoid neoplasms.

Cyclin D1 is an oncogene frequently overexpressed in human cancers that has a dual function as cell cycle and transcriptional regulator, although the latter is widely unexplored. Here, we investigated the transcriptional role of cyclin D1 in lymphoid tumor cells with cyclin D1 oncogenic overexpression. Cyclin D1 showed widespread binding to the promoters of most actively transcribed genes, and the promoter occupancy positively correlated with the transcriptional output of targeted genes. Despite this association, the overexpression of cyclin D1 in lymphoid cells led to a global transcriptional downmodulation that was proportional to cyclin D1 levels. This cyclin D1-dependent global transcriptional downregulation was associated with a reduced nascent transcription and an accumulation of promoter-proximal paused RNA polymerase II (Pol II) that colocalized with cyclin D1. Concordantly, cyclin D1 overexpression promoted an increase in the Poll II pausing index. This transcriptional impairment seems to be mediated by the interaction of cyclin D1 with the transcription machinery. In addition, cyclin D1 overexpression sensitized cells to transcription inhibitors, revealing a synthetic lethality interaction that was also observed in primary mantle cell lymphoma cases. This finding of global transcriptional dysregulation expands the known functions of oncogenic cyclin D1 and suggests the therapeutic potential of targeting the transcriptional machinery in cyclin D1-overexpressing tumors.