Component Of Super Elongation Complex Research Articles

ATM-mediated ELL phosphorylation enhances its self-association through increased EAF1 interaction and inhibits global transcription during genotoxic stress.

Mammalian cells immediately inhibit transcription upon exposure to genotoxic stress to avoid fatal collision between ongoing transcription and newly recruited DNA repair machineries to protect genomic integrity. However, mechanisms of this early transcriptional inhibition are poorly understood. In this study, we decipher a novel role of human EAF1, a positive regulator of ELL-dependent RNA Polymerase II-mediated transcription in vitro, in regulation of temporal inhibition of transcription during genotoxic stress. Our results show that, besides Super Elongation Complex (SEC) and Little Elongation Complex (LEC), human ELL (aka ELL1) also forms a complex with EAF1 alone. Interestingly, contrary to the in vitro studies, EAF1 inhibits ELL-dependent RNA polymerase II-mediated transcription of diverse target genes. Mechanistically, we show that intrinsic self-association property of ELL leads to its reduced interaction with other SEC components. EAF1 enhances ELL self-association and thus reduces its interaction with other SEC components leading to transcriptional inhibition. Physiologically, we show that upon exposure to genotoxic stress, ATM-mediated ELL phosphorylation-dependent enhanced EAF1 association results in reduced ELL interaction with other SEC components that lead to global transcriptional inhibition. Thus, we describe an important mechanism of dynamic transcriptional regulation during genotoxic stress involving post-translational modification of a key elongation factor.

AFF4 Predicts the Prognosis of Colorectal Cancer Patients and Suppresses Colorectal Cancer Metastasis via Promoting CDH1 Expression.

IntroductionAF4/FMR2 family member 4 (AFF4) is a core component of super elongation complex (SEC) and regulates the transcription elongation of many genes. AFF4 depletion or amplification is associated with multiple cancers, but its role in colorectal cancer (CRC) has not been investigated so far.MethodsqRT-PCR and Western blot analyzed AFF4 expression in the paired clinical CRC tissues. The patients’ overall survival curve was determined using the Kaplan-Meier plotter. In vitro experiments, such as cell proliferation, migration, and invasion, were used to preliminarily ascertain the role of AFF4 in CRC. A CRC cell liver metastasis animal model was well established. Livers were harvested and examined histologically by a series of indicators, such as tumor nodules, liver weight, ALT/AST activity, and tumor cell identification by hematoxylin-eosin (HE) staining.ResultsWe firstly examined the expression of AFF4 in colorectal cancer and normal tissues by collecting paired CRC tissues and adjacent normal tissues, revealing that AFF4 was significantly downregulated in CRC patients and lower expression of AFF4 was correlated with poor prognosis. Next, we observed that presence or absence of AFF4 in CRC cells had no effect on cancer cell proliferation, while AFF4 depletion significantly promoted the migration or invasion of CRC cells in vitro. Furthermore, we confirmed that AFF4 deficiency enhanced the metastatic capacity of CRC cells in vivo. Mechanistically, we found that AFF4 upregulated the transcription of CDH1 gene, which encodes E-cadherin and suppresses the epithelial-mesenchymal transition (EMT). Knockdown of AFF4 interfered with CDH1 transcription, resulting in downregulation of E-cadherin expression and the progression of CRC. Moreover, restored CDH1 expression could rescue the phenotype of CRC cells without AFF4.ConclusionsCollectively, our data demonstrated that AFF4 served as a significant novel regulator of CRC via CDH1 transcriptional regulation and a potential effective therapy target for patients with CRC.

The Expression and Roles of the Super Elongation Complex in Mouse Cochlear Lgr5+ Progenitor Cells.

The super elongation complex (SEC) has been reported to play a key role in the proliferation and differentiation of mouse embryonic stem cells. However, the expression pattern and function of the SEC in the inner ear has not been investigated. Here, we studied the inner ear expression pattern of three key SEC components, AFF1, AFF4, and ELL3, and found that these three proteins are all expressed in both cochlear hair cells (HCs)and supporting cells (SCs). We also cultured Lgr5+ inner ear progenitors in vitro for sphere-forming assays and differentiation assays in the presence of the SEC inhibitor flavopiridol. We found that flavopiridol treatment decreased the proliferation ability of Lgr5+ progenitors, while the differentiation ability of Lgr5+ progenitors was not affected. Our results suggest that the SEC might play important roles in regulating inner ear progenitors and thus regulating HC regeneration. Therefore, it will be very meaningful to further investigate the detailed roles of the SEC signaling pathway in the inner ear in vivo in order to develop effective treatments for sensorineural hearing loss.

Therapeutic targeting of transcriptional elongation in diffuse intrinsic pontine glioma.

Diffuse intrinsic pontine glioma (DIPG) is associated with transcriptional dysregulation driven by H3K27 mutation. The super elongation complex (SEC) is required for transcriptional elongation through release of RNA polymerase II (Pol II). Inhibition of transcription elongation by SEC disruption can be an effective therapeutic strategy of H3K27M-mutant DIPG. Here, we tested the effect of pharmacological disruption of the SEC in H3K27M-mutant DIPG to advance understanding of the molecular mechanism and as a new therapeutic strategy for DIPG. Short hairpin RNAs (shRNAs) were used to suppress the expression of AF4/FMR2 4 (AFF4), a central SEC component, in H3K27M-mutant DIPG cells. A peptidomimetic lead compound KL-1 was used to disrupt a functional component of SEC. Cell viability assay, colony formation assay, and apoptosis assay were utilized to analyze the effects of KL-1 treatment. RNA- and ChIP-sequencing were used to determine the effects of KL-1 on gene expression and chromatin occupancy. We treated mice bearing H3K27M-mutant DIPG patient-derived xenografts (PDXs) with KL-1. Intracranial tumor growth was monitored by bioluminescence image and therapeutic response was evaluated by animal survival. Depletion of AFF4 significantly reduced the cell growth of H3K27M-mutant DIPG. KL-1 increased genome-wide Pol II occupancy and suppressed transcription involving multiple cellular processes that promote cell proliferation and differentiation of DIPG. KL-1 treatment suppressed DIPG cell growth, increased apoptosis, and prolonged animal survival with H3K27M-mutant DIPG PDXs. SEC disruption by KL-1 increased therapeutic benefit in vitro and in vivo, supporting a potential therapeutic activity of KL-1 in H3K27M-mutant DIPG.

Dynamic regulation of promoter-proximal RNA polymerase II pausing

Transcriptional pausing is a widely used regulatory mechanism to control precise gene expression from bacteria to humans. In metazoans, transcription initiation requires the recruitment of general transcription factors and RNA polymerase II (Pol II) to gene promoters. After it initiates transcription and synthesizes a short RNA, Pol II pauses at the promoter-proximal region, standing by for further cues to enter the productive elongation stage. Promoter-proximal Pol II pausing is one of the rate-limiting steps during transcription, functioning as an early transcriptional elongation check point, to ensure the correct modification of transcription machinery and the addition of the 7-methylguanosine cap to nascent transcripts. Pol II pausing at promoter-proximal region is stabilized by the negative elongation factor (NELF) and the 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor (DSIF). In response to developmental signals or environmental stress, the release of paused Pol II can be triggered by the positive transcription elongation factor b (P-TEFb), which is composed of the kinase CDK9 and its regulatory subunit CCNT1/2. The kinase activity of P-TEFb towards Pol II carboxy-terminal domain (CTD), NELF and DSIF is critical for P-TEFb to execute its function in pause release, and is thus tightly controlled. To date, it has been identified that P-TEFb mainly exists in three different complexes: the super elongation complex (SEC), BRD4-P-TEFb, and the inactive 7SK snRNP-P-TEFb complex. SEC, one of the most active P-TEFb containing complexes, is required for rapid gene expression in response to stress or developmental signals. The active and inactive forms of P-TEFb complexes co-exist in vivo , reaching equilibrium to meet the transcriptional needs of cells. The transition of Pol II from pause to productive elongation stage is achieved by dynamic exchange between the pausing factors and the positive elongation factors at the proximal promoter region. Liquid-liquid phase separation (LLPS) in living cells is a physicochemical process that confines biochemical reactions within membrane-less compartments. Low complexity intrinsically disordered regions (IDRs) within proteins can initiate and promote phase separation and formation of liquid droplets, which in turn facilitate the multivalent weak interactions among these IDR-containing proteins. Recent studies using super-resolution live cell imaging technology have revealed that RNA Pol II can form dynamic foci in cells through LLPS and transitions between different phases, which are likely mediated by phosphorylated CTD. Moreover, factors involved in various transcription steps can rapidly and dynamically concentrate and exchange at the hot regulatory genomic loci. For example, SEC components are able to compartmentalize and concentrate P-TEFb from its inactive partners. Upon serum stimulation, SEC assembles promptly into phase-separated droplets at the immediate early genes (IEG), triggering rapid transcription induction. Mutations in transcription regulators can lead to developmental defects and many human diseases, including cancers. For instance, abnormal stabilization of SEC components via MLL fusion plays a contributing role in leukemogenesis. Fusion of the SEC core component ENL with MLL can greatly enhance phase separation of SEC, through which the leukemic genes might be mis-activated. In addition, there is growing evidence that disease related mutations in transcriptional regulators can cause malfunction through aberrant condensation, providing potential targets for designing therapeutic strategies through phase separation interventions.

AFF4 enhances odontogenic differentiation of human dental pulp cells

AFF4 is a component of super elongation complex (SECs) and functions as a scaffold protein to bridge the transcription elongation factors. It is associated with leukemia, HIV transcription, and head neck cancer. However, its role in odontogenic differentiation of dental pulp cells (DPCs) is unclear. Here, we show the expression of AFF4 is increased during odontogenesis. Depletion of AFF4 in human DPCs leads to a decrease of alkaline phosphatase (ALP) activity, calcium mineralization and odontogenic-related genes expression. On the contrary, Lentivirus-mediated overexpression of AFF4 induces the odontogenic potential of DPCs. Mechanistically, we found AFF4 regulates the transcription of NFIC, a key factor for tooth root formation. Overexpression of NFIC successfully rescues the restricted differentiation of AFF4-depleted cells. Our data demonstrate that AFF4 serves as a previously unknown regulator of odontogenesis.

ELL-associated factors EAF1/2 negatively regulate HIV-1 transcription through inhibition of Super Elongation Complex formation

The ELL (ELL1 and ELL2)-containing Super Elongation Complex (SEC) is required for efficient HIV-1 transactivation by the viral-encoded Tat protein. EAF1 and EAF2 are ELL-associated factors and considered as positive regulators of ELL. However, their role in HIV-1 transcriptional control is unknown. In this study, we show that EAF1/2 inhibit the SEC-dependent and Tat-activated HIV-1 transcription. EAF1/2 are found to interact with the SEC components in an ELL1/2-dependent manner. Surprisingly, the depletion of EAF1/2 increases the SEC formation and occupancy on the HIV-1 proviral DNA, thereby stimulating Tat transactivation of HIV-1. Although EAF1/2 interact with members of the SEC in a ELL-dependent manner, this interaction competes with the binding of the scaffolding subunit AFF1 with ELL, thus reducing the SEC formation. Together, these data reveal how EAF1/2 regulate the SEC formation to control HIV-1 transcription.

AFF1 acetylation by p300 temporally inhibits transcription during genotoxic stress response

Soon after exposure to genotoxic reagents, mammalian cells inhibit transcription to prevent collisions with repair machinery and to mount a proper DNA damage response. However, mechanisms underlying early transcriptional inhibition are poorly understood. In this report, we show that site-specific acetylation of super elongation complex (SEC) subunit AFF1 by p300 reduces its interaction with other SEC components and impairs P-TEFb-mediated C-terminal domain phosphorylation of RNA polymerase II both in vitro and in vivo. Reexpression of wild-type AFF1, but not an acetylation mimic mutant, restores SEC component recruitment and target gene expression in AFF1 knockdown cells. Physiologically, we show that, upon genotoxic exposure, p300-mediated AFF1 acetylation is dynamic and strongly correlated with concomitant global down-regulation of transcription-and that this can be reversed by overexpression of an acetylation-defective AFF1 mutant. Therefore, we describe a mechanism of dynamic transcriptional regulation involving p300-mediated acetylation of a key elongation factor during genotoxic stress.

Abstract 3125: SOX2 controls the tumor initiation and development and acts as a prognostic predictor of oral squamous cell carcinoma

Abstract Background: Sex determining region Y-BOX2 (SOX2), a regulator of the self-renewal ability of stem cells, plays a compelling role in initiation and development of cancer. However, little is known about the role and network controlling of SOX2 in oral squamous cell carcinoma (OSCC) development. Method: In this study, we conducted a retrospective cohort of 229 OSCC patients from two independent Chinese centers from May 2003 to August 2012. SOX2 expression in these samples was determined by immunostaining. Univariate and multivariate analyses were performed. Then we generated SOX2-creERT2 mice that expressing an inducible Cre recombinase under the control of a minimal promoter of SOX2, along with a tdTomato reporter. These mice were exposed to low dose 4NQO in the drinking water either for 8, 12 or 16 weeks. We further investigate the network controlling of SOX2 by ChIP assay. Then we detected the expression of SOX2 in response to AFF4 knockdown and overexpression by western blot, respectively. Furthermore, we used wound-healing, transwell, sphere formation and limiting dilution assay to confirm whether SOX2 expression was regulated by AFF4. Results: In the multiple cohorts, high SOX2 protein expression was negatively correlated with the overall survival for OSCC patients. Impressively, we found chemotherapy only improved outcomes of patients with low SOX2 expression, but very limited effects to high SOX2 expression patients. Meanwhile low SOX2 expression patients had significantly better survival with rather than without chemotherapies. Lineage tracing study in vivo suggested that SOX2 positive cells play an important role in the carcinogenesis of OSCC as epithelial stem cells. Increasing SOX2 positive cells and their daughter cells was a major trigger in the initiation of OSCC. Mechanistically, we found SOX2 was regulated by AFF4, the core component of Super elongation complex (SEC) to promote the proliferation, migration and invasion of OSCC cells. SOX2 expression changed in parallel with AFF4 expression in response to depletion and overexpression of AFF4, respectively. More importantly, the inhibited proliferation, migration, invasion and ALDH activity induced by knockdown of AFF4 in OSCC cells were rescued by overexpression of SOX2. Conclusion: Collectively, our findings indicate SOX2 acts as a prognostic predictor and controls the tumor initiation and development in oral squamous cell carcinoma. SOX2 may serve as a potential target of therapies for patients with OSCC. Note: This abstract was not presented at the meeting. Citation Format: ZIHAO WEI, FENGYING YIN, PENG DENG, XUEFENG ZHANG, JING DENG, JING LI, LIANG XIE, QIANMING CHEN. SOX2 controls the tumor initiation and development and acts as a prognostic predictor of oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3125.

Multivalent Role of Human TFIID in Recruiting Elongation Components at the Promoter-Proximal Region for Transcriptional Control

Despite substantial progress in our understanding of the players involved and the regulatory mechanisms controlling the initiation and elongation steps of transcription, little is known about the recruitment of elongation factors at promoter-proximal regions for the initiation-to-elongation transition. Here, we show evidence that human TFIID, which initiates pre-initiation complex (PIC) assembly, contributes to regulating the recruitment of super-elongation complex (SEC) components at the promoter-proximal region through interactions among selective TAF and SEC components. Invitro direct interactions, coupled with cell-based assays, identified an important poly-Ser domain within SEC components that are involved in their interaction with TFIID. DNA template-based recruitment assays, using purified components, further show a direct role for poly-Ser domain-dependent TFIID interaction in recruiting SEC components on target DNA. Consistently, ChIP and RNA analyses have shown the importance of this mechanism in TFIID-dependent SEC recruitment and target gene expression within mammalian cells.

AFF4 promotes tumorigenesis and tumor-initiation capacity of head and neck squamous cell carcinoma cells by regulating SOX2.

Super elongation complex (SEC) controls gene transcription by releasing Pol II from pausing. Previous studies have shown that dysfunction of SEC was associated with multiple human cancers, such as leukemia and breast cancer. However, the role of SEC in head and neck squamous cell carcinoma (HNSCC) development remains largely unknown. In this study, we found expression of AF4/FMR2 family member 4 (AFF4), the core component of SEC, was upregulated dramatically in HNSCC cell lines and tumor tissues. By using siRNA-mediated depletion and overexpression of AFF4, we demonstrated AFF4 promoted proliferation, migration and invasion of HNSCC cells. Moreover, we found AFF4 enhanced the aldehyde dehydrogenase (ALDH) activity and sphere formatting activity and was required for the tumor-initiation capacity of stem-like cells in HNSCC cell lines. Mechanistically, we found the role of AFF4 in regulation of HNSCC cell behaviors was mainly mediated by sex-determining region Y box2 (SOX2), a critical regulator involved in development of several human cancers. SOX2 expression changed in parallel with AFF4 expression in response to depletion and overexpression of AFF4, respectively. More importantly, overexpression of SOX2 rescued the inhibited proliferation, migration, invasion and ALDH activity induced by knockdown of AFF4 in HNSCC cells, at least in part. Collectively, our findings indicate AFF4 may serve as a biomarker and a potential target of therapies for patients with HNSCC.

P-TEFb, the super elongation complex and mediator regulate a subset of non-paused genes during early Drosophila embryo development.

Positive Transcription Elongation Factor b (P-TEFb) is a kinase consisting of Cdk9 and Cyclin T that releases RNA Polymerase II (Pol II) into active elongation. It can assemble into a larger Super Elongation Complex (SEC) consisting of additional elongation factors. Here, we use a miRNA-based approach to knock down the maternal contribution of P-TEFb and SEC components in early Drosophila embryos. P-TEFb or SEC depletion results in loss of cells from the embryo posterior and in cellularization defects. Interestingly, the expression of many patterning genes containing promoter-proximal paused Pol II is relatively normal in P-TEFb embryos. Instead, P-TEFb and SEC are required for expression of some non-paused, rapidly transcribed genes in pre-cellular embryos, including the cellularization gene Serendipity-α. We also demonstrate that another P-TEFb regulated gene, terminus, has an essential function in embryo development. Similar morphological and gene expression phenotypes were observed upon knock down of Mediator subunits, providing in vivo evidence that P-TEFb, the SEC and Mediator collaborate in transcription control. Surprisingly, P-TEFb depletion does not affect the ratio of Pol II at the promoter versus the 3’ end, despite affecting global Pol II Ser2 phosphorylation levels. Instead, Pol II occupancy is reduced at P-TEFb down-regulated genes. We conclude that a subset of non-paused, pre-cellular genes are among the most susceptible to reduced P-TEFb, SEC and Mediator levels in Drosophila embryos.

Abstract SY38-03: Inhibition of BET recruitment to chromatin as an effective treatment for MLL-fusion leukemia

Abstract Inhibition of BET recruitment to chromatin as an effective treatment for MLL-fusion leukemia Recurrent chromosomal translocations involving the mixed lineage leukemia (MLL) gene initiate aggressive forms of leukemia, which are often refractory to conventional therapies. Many MLL-fusion partners are members of the super elongation complex (SEC), a critical regulator of transcriptional elongation, suggesting that aberrant control of this process plays an important role in leukemia induction. Here we will describe a global proteomic strategy to demonstrate that MLL-fusions, as part of SEC and the polymerase associated factor (PAFc) complex are associated with the BET family of acetyl-lysine recognising, chromatin “adaptor” proteins. These data provided the basis for therapeutic intervention in MLL-fusion leukemia, via the displacement of the BET family of proteins from chromatin. We will show that a novel small molecule inhibitor of the BET family GSK1210151A (I-BET151) has profound efficacy against human and murine MLL-fusion leukemic cell lines, through the induction of early cell cycle arrest and apoptosis. I-BET151 treatment in two human leukemia cell lines with different MLL-fusions alters the expression of a common set of genes whose function may account for these phenotypic changes. The mode of action of I-BET151 is, at least in part, due to the inhibition of transcription at key genes (BCL2, C-MYC and CDK6) through the displacement of BRD3/4, PAFc and SEC components from chromatin. In vivo studies will demonstrate that I-BET151 has significant therapeutic value, providing survival benefit in two distinct mouse models of murine MLL-AF9 and human MLL-AF4 leukemia. In addition, the efficacy of I-BET151 against human leukemia stem cells (LSC) will be shown, providing further evidence of its potent therapeutic potential. These findings establish the displacement of BET proteins from chromatin as a promising epigenetic therapy for these aggressive leukemias. To extend the applications of our work, we will also present preliminary data to demonstrate that inhibition of BET proteins has therapeutic promise in a larger number of AML subtypes. We will speculate on potential mechanisms for this, the investigation of which is ongoing. Finally, we will discuss extension of the paradigm of BET inhibition to the numerous other epigenetic “readers” implicated in the induction and progression of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY38-03. doi:1538-7445.AM2012-SY38-03

ELL facilitates RNA polymerase II pause site entry and release

Transcription is a multi-stage process that coordinates several steps within the transcription cycle including chromatin reorganization, RNA polymerase II recruitment, initiation, promoter clearance and elongation. Recent advances have identified the super elongation complex, containing the eleven-nineteen lysine-rich leukaemia (ELL) protein, as a key regulator of transcriptional elongation. Here we show that ELL has a diverse and kinetically distinct role before its assembly into the super elongation complex by stabilizing Pol II recruitment/initiation and entry into the pause site. Loss of ELL destabilizes the pre-initiation complexes and results in disruption of early elongation and promoter proximal chromatin structure before recruitment of AFF4 and other super elongation complex components. These changes result in significantly reduced transcriptional activation of rapidly induced genes. Thus, ELL has an early and essential role during rapid high-amplitude gene expression that is required for both Pol II pause site entry and release.

Inhibition of BET recruitment to chromatin as an effective treatment for MLL-fusion leukaemia.

Recurrent chromosomal translocations involving the mixed lineage leukaemia (MLL) gene initiate aggressive forms of leukaemia, which are often refractory to conventional therapies. Many MLL-fusion partners are members of the super elongation complex (SEC), a critical regulator of transcriptional elongation, suggesting that aberrant control of this process has an important role in leukaemia induction. Here we use a global proteomic strategy to demonstrate that MLL fusions, as part of SEC and the polymerase-associated factor complex (PAFc), are associated with the BET family of acetyl-lysine recognizing, chromatin 'adaptor' proteins. These data provided the basis for therapeutic intervention in MLL-fusion leukaemia, via the displacement of the BET family of proteins from chromatin. We show that a novel small molecule inhibitor of the BET family, GSK1210151A (I-BET151), has profound efficacy against human and murine MLL-fusion leukaemic cell lines, through the induction of early cell cycle arrest and apoptosis. I-BET151 treatment in two human leukaemia cell lines with different MLL fusions alters the expression of a common set of genes whose function may account for these phenotypic changes. The mode of action of I-BET151 is, at least in part, due to the inhibition of transcription at key genes (BCL2, C-MYC and CDK6) through the displacement of BRD3/4, PAFc and SEC components from chromatin. In vivo studies indicate that I-BET151 has significant therapeutic value, providing survival benefit in two distinct mouse models of murine MLL-AF9 and human MLL-AF4 leukaemia. Finally, the efficacy of I-BET151 against human leukaemia stem cells is demonstrated, providing further evidence of its potent therapeutic potential. These findings establish the displacement of BET proteins from chromatin as a promising epigenetic therapy for these aggressive leukaemias.

The Eleven-Nineteen Lysine-rich Leukemia Gene (ELL2) Influences the Histone H3 Protein Modifications Accompanying the Shift to Secretory Immunoglobulin Heavy Chain mRNA Production

In plasma cells, immunoglobulin heavy chain (IgH) secretory-specific mRNA is made in high abundance as a result of both increased promoter proximal poly(A) site choice and weak splice-site skipping. Ell2, the eleven-nineteen lysine rich leukemia gene, is a transcription elongation factor that is induced ∼6-fold in plasma cells and has been shown to drive secretory-specific mRNA production. Reducing ELL2 by siRNA, which reduced processing to the secretion-specific poly(A) site, also influenced the methylations of histone H3K4 and H3K79 on the IgH gene and impacted positive transcription factor b (pTEFb), Ser-2 carboxyl-terminal phosphorylation, and polyadenylation factor additions to RNA polymerase II. The multiple lineage leukemia gene (MLL) and Dot1L associations with the IgH gene were also impaired in the absence of ELL2. To investigate the link between histone modifications, transcription elongation, and alternative RNA processing in IgH mRNA production, we performed chromatin immunoprecipitation on cultured mouse B and plasma cells bearing the identical IgH γ2a gene. In the plasma cells, as compared with the B cells, the H3K4 and H3K79 methylations extended farther downstream, past the IgH enhancer to the end of the transcribed region. Thus the downstream H3K4 and H3K79 methylation of the IgH associated chromatin in plasma cells is associated with increased polyadenylation and exon skipping, resulting from the actions of ELL2 transcription elongation factor.