Project description:P-TEFb, a heterodimer of kinase, CDK9, and Cyclin T1, is a critical regulator of promoter-proximal pause release of Pol II in metazoans. It is capable of forming three larger multiprotein complexes, including the super elongation complex (SEC), the BRD4/P-TEFb complex and the 7SK snRNP. In the SEC or the BRD4/P-TEFb, P-TEFb is enzymatically active, while in the 7SK snRNP, its activity is inhibited. The SEC consists of AFF1 or 4, ENL or AF9, ELL1, 2 or 3 and EAF1 or 2 in addition to P-TEFb, the only subunit with catalytic activity, and the noncatalytic subunits have been found to be able to regulate pause release through P-TEFb. One recent study showed that in human DLD-1 cells, the SEC only regulates pause release of heat shock (HS) genes, whereas the BRD4/P-TEFb complex regulates pause release of the rest of the genes. In this study, we found that AFF4 knockdown in human HEL cells decreased not only cellular level but also global chromatin occupancy of CTD serine 2 phosphorylated Pol II, and notably, increased promoter-proximal pause of Pol II on several hundred HS and thousands of non-HS genes. Mechanistically, AFF4 facilitates pause release likely by facilitating the binding of P-TEFb to Pol II. These results suggest that the extent of impact of AFF4 on pause release is likely to be context-dependent or cell-type dependent.
Project description:P-TEFb, a heterodimer of kinase, CDK9, and Cyclin T1, is a critical regulator of promoter-proximal pause release of Pol II in metazoans. It is capable of forming three larger multiprotein complexes, including the super elongation complex (SEC), the BRD4/P-TEFb complex and the 7SK snRNP. In the SEC or the BRD4/P-TEFb, P-TEFb is enzymatically active, while in the 7SK snRNP, its activity is inhibited. The SEC consists of AFF1 or 4, ENL or AF9, ELL1, 2 or 3 and EAF1 or 2 in addition to P-TEFb, the only subunit with catalytic activity, and the noncatalytic subunits have been found to be able to regulate pause release through P-TEFb. One recent study showed that in human DLD-1 cells, the SEC only regulates pause release of heat shock (HS) genes, whereas the BRD4/P-TEFb complex regulates pause release of the rest of the genes. In this study, we found that AFF4 knockdown in human HEL cells decreased not only cellular level but also global chromatin occupancy of CTD serine 2 phosphorylated Pol II, and notably, increased promoter-proximal pause of Pol II on several hundred HS and thousands of non-HS genes. Mechanistically, AFF4 facilitates pause release likely by facilitating the binding of P-TEFb to Pol II. These results suggest that the extent of impact of AFF4 on pause release is likely to be context-dependent or cell-type dependent.
Project description:P-TEFb, a heterodimer of kinase, CDK9, and Cyclin T1, is a critical regulator of promoter-proximal pause release of Pol II in metazoans. It is capable of forming three larger multiprotein complexes, including the super elongation complex (SEC), the BRD4/P-TEFb complex and the 7SK snRNP. In the SEC or the BRD4/P-TEFb, P-TEFb is enzymatically active, while in the 7SK snRNP, its activity is inhibited. The SEC consists of AFF1 or 4, ENL or AF9, ELL1, 2 or 3 and EAF1 or 2 in addition to P-TEFb, the only subunit with catalytic activity, and the noncatalytic subunits have been found to be able to regulate pause release through P-TEFb. One recent study showed that in human DLD-1 cells, the SEC only regulates pause release of heat shock (HS) genes, whereas the BRD4/P-TEFb complex regulates pause release of the rest of the genes. In this study, we found that AFF4 knockdown in human HEL cells decreased not only cellular level but also global chromatin occupancy of CTD serine 2 phosphorylated Pol II, and notably, increased promoter-proximal pause of Pol II on several hundred HS and thousands of non-HS genes. Mechanistically, AFF4 facilitates pause release likely by facilitating the binding of P-TEFb to Pol II. These results suggest that the extent of impact of AFF4 on pause release is likely to be context-dependent or cell-type dependent.
Project description:AFF4 is a component of super elongation complex (SEC), which plays an important role in mobilizing paused RNA polymerase II at gene promoter regions. Using exome sequenging, we have identified a novel genetic disorder caused by missense mutations in AFF4. We propose CHOPS syndrome as a name for this new diagnosis. To evaluate the effect of identified missense mutations of AFF4, utilizing patient derived skin fibroblast cell lines, the gene expression analysis was perfomred.
Project description:AFF4 is a component of super elongation complex (SEC), which plays an important role in mobilizing paused RNA polymerase II at gene promoter regions. Using exome sequenging, we have identified a novel genetic disorder caused by missense mutations in AFF4. We propose CHOPS syndrome as a name for this new diagnosis. To evaluate the effect of identified missense mutations of AFF4, utilizing patient derived skin fibroblast cell lines, the gene expression analysis was perfomred. To characterize the transcriptome pattern observed in CHOPS syndrome, the skin fibroblast samples from two CHOPS syndrome probands and three healthy control subjects were used. Samples used for expression array include two CHOPs syndrome samples (CDL160: 6 year-old Caucasian female with 254S mut and CDL444: 12 year-old Caucasian male with 254A mut) and three age gender matched controls (GM01652: 11 year-old Caucasian female, GM02036 11 year-old Caucasian female and GM08398: 8 year-old Caucasian male).
Project description:A correlation between histone acetylation and transcription has been noted for a long time, but little is known about what step(s) in the transcription cycle is influenced by acetylation. Here, we have examined the immediate transcriptional response to histone deacetylase (HDAC) inhibition, and find that release of promoter-proximal paused RNA polymerase II (Pol II) into elongation is stimulated, whereas recruitment to gene promoters is not. Although histone acetylation is elevated globally by HDAC inhibition, less than 100 genes respond within 10 min. These genes are highly paused, are strongly associated with the chromatin regulators NURF and Trithorax, display a greater increase in acetylation of the first nucleosomes than other genes, and become transcriptionally activated by HDAC inhibition. Among these rapidly upregulated genes are HDAC1 (Rpd3) and subunits of HDAC-containing co-repressor complexes, demonstrating feedback regulation upon HDAC inhibition. Our results suggest that histone acetylation stimulates transcription of paused genes, and that increased acetylation is not a consequence of their enhanced expression.