Project description:The elongation stage of transcription is a highly regulated in metazoan. We previously purified the AFF1/AFF4-containing Super Elongation Complex (SEC) as a major regulator of development and cancer pathogenesis. Here, we report the biochemical isolation of SEC-like 2 (SEC-L2) and SEC-like 3 (SEC-L3) containing AFF2 and AFF3 in association with P-TEFb, ENL, and AF9. The SEC family members demonstrate high levels of Pol II CTD kinase activity, however, only SEC is required for the proper induction of the HSP70 gene upon stress. Genome-wide mRNA-seq analyses demonstrate that SEC-L2-3 control the expression of different subsets of genes, while AFF4/SEC plays a more dominant role in rapid gene expression in cells. MYC is one of the direct targets of AFF4/SEC, and the SEC requirement to the MYC gene regulates its expression in different cancer cells bearing either acute myeloid or lymphoid leukemia. These findings suggest that AFF4/SEC could be a potential therapeutic target for the treatment of leukemia or other cancers associated with MYC overexpression. RNA-seq in human embyonic kidney 293T cells of wild-type and after RNAi of AFF2, AFF3, AFF4. ChIP-seq of AFF4 and Pol2 in human 293T cells.
Project description:The AF4/FMR2 proteins AFF1 and AFF4 act as a scaffold to assemble the Super Elongation Complex (SEC) that strongly activates transcriptional elongation of HIV-1 and cellular genes. Although they can dimerize, it is unclear whether the dimers exist and function within a SEC in vivo. Furthermore, it is unknown whether AFF1 and AFF4 function similarly in mediating SEC-dependent activation of diverse genes. Providing answers to these questions, our current study shows that AFF1 and AFF4 reside in separate SECs that display largely distinct gene target specificities. While the AFF1-SEC is more potent in supporting HIV-1 transactivation by the viral Tat protein, the AFF4-SEC is more important for HSP70 induction upon heat shock. The functional difference between AFF1 and AFF4 in Tat-transactivation has been traced to a single amino acid variation between the two proteins, which causes them to enhance the affinity of Tat for P-TEFb, a key SEC component, with different efficiency. Finally, genome-wide analysis confirms that the genes regulated by AFF1- and AFF4-SEC are largely non-overlapping and perform distinct functions. Thus, the SEC represents a family of related complexes that exist to increase the regulatory diversity and gene control options during transactivation of diverse cellular and viral genes. RNA-seq in HeLa cells of wild-type and after RNAi of AFF1 or AFF4.
Project description:The super elongation complex (SEC) is required for robust and productive transcription through release of RNA polymerase II (Pol II) with its P-TEFb module and promoting transcriptional processivity with its ELL2 subunit. Malfunction of SEC contributes to multiple human diseases including cancer. Here, we identify peptidomimetic lead compounds, KL-1 and its structural homolog KL-2, which disrupt the interaction between the SEC scaffolding protein AFF4 and P-TEFb, resulting in impaired release of Pol II from promoter-proximal pause sites and a reduced average rate of processive transcription elongation. SEC is required for induction of heat-shock genes and treating cells with KL-1 and KL-2 attenuates the heat-shock response from Drosophila to human. SEC inhibition downregulates MYC and MYC-dependent transcriptional programs in mammalian cells and delays tumor progression in a mouse xenograft model of MYC-driven cancer, indicating that small-molecule disruptors of SEC could be used for targeted therapy of MYC-induced cancer.
Project description:The elongation stage of transcription is a highly regulated in metazoan. We previously purified the AFF1/AFF4-containing Super Elongation Complex (SEC) as a major regulator of development and cancer pathogenesis. Here, we report the biochemical isolation of SEC-like 2 (SEC-L2) and SEC-like 3 (SEC-L3) containing AFF2 and AFF3 in association with P-TEFb, ENL, and AF9. The SEC family members demonstrate high levels of Pol II CTD kinase activity, however, only SEC is required for the proper induction of the HSP70 gene upon stress. Genome-wide mRNA-seq analyses demonstrate that SEC-L2-3 control the expression of different subsets of genes, while AFF4/SEC plays a more dominant role in rapid gene expression in cells. MYC is one of the direct targets of AFF4/SEC, and the SEC requirement to the MYC gene regulates its expression in different cancer cells bearing either acute myeloid or lymphoid leukemia. These findings suggest that AFF4/SEC could be a potential therapeutic target for the treatment of leukemia or other cancers associated with MYC overexpression.
Project description:Due to their unique longevity and capacity to secrete high levels of protein, plasma B cells play have the potential to be used as a cell therapy for protein replacement. Here, we show that ex vivo engineered human plasma cells exhibited transcriptional features of long-lived plasma cells.
Project description:To test whether Brd4 and SEC co-regulate the release of promoter-proximally paused Pol II, we performed Pol II ChIP-Seq to analyze the effect of depletion of Brd4 or SEC on HMBA-induced pause release in HCT116 cells.
