Project description:The MYC transcription factor is an unstable protein and its turnover is controlled by the ubiquitin system. Ubiquitination enhances MYC-dependent transactivation, but the underlying mechanism remains unresolved. Here we show that proteasomal turnover of MYC is dispensable for recruitment of RNA polymerase II (RNAPII), but is required to promote transcriptional elongation at MYC target genes. Degradation of MYC stimulates histone acetylation and recruitment of BRD4 and P-TEFb to target promoters, leading to phosphorylation of RNAPII CTD and the release of elongating RNAPII. In the absence of degradation, the RNA polymerase II-associated factor (PAF) complex associates with MYC via interaction of its CDC73 subunit with a conserved domain in the amino-terminus of MYC ("MYC box I"), suggesting that a MYC/PAF complex is an intermediate in transcriptional activation. Since histone acetylation depends on a second highly conserved domain in MYCs amino-terminus ("MYC box II"), we propose that both domains co-operate to transfer elongation factors onto paused RNAPII.
Project description:The MYC transcription factor is an unstable protein and its turnover is controlled by the ubiquitin system. Ubiquitination enhances MYC-dependent transactivation, but the underlying mechanism remains unresolved. Here we show that proteasomal turnover of MYC is dispensable for recruitment of RNA polymerase II (RNAPII), but is required to promote transcriptional elongation at MYC target genes. Degradation of MYC stimulates histone acetylation and recruitment of BRD4 and P-TEFb to target promoters, leading to phosphorylation of RNAPII CTD and the release of elongating RNAPII. In the absence of degradation, the RNA polymerase II-associated factor (PAF) complex associates with MYC via interaction of its CDC73 subunit with a conserved domain in the amino-terminus of MYC ("MYC box I"), suggesting that a MYC/PAF complex is an intermediate in transcriptional activation. Since histone acetylation depends on a second highly conserved domain in MYCs amino-terminus ("MYC box II"), we propose that both domains co-operate to transfer elongation factors onto paused RNAPII.
Project description:The MYC transcription factor is an unstable protein and its turnover is controlled by the ubiquitin system. Ubiquitination enhances MYC-dependent transactivation, but the underlying mechanism remains unresolved. Here we show that proteasomal turnover of MYC is dispensable for recruitment of RNA polymerase II (RNAPII), but is required to promote transcriptional elongation at MYC target genes. Degradation of MYC stimulates histone acetylation and recruitment of BRD4 and P-TEFb to target promoters, leading to phosphorylation of RNAPII CTD and the release of elongating RNAPII. In the absence of degradation, the RNA polymerase II-associated factor (PAF) complex associates with MYC via interaction of its CDC73 subunit with a conserved domain in the amino-terminus of MYC ("MYC box I"), suggesting that a MYC/PAF complex is an intermediate in transcriptional activation. Since histone acetylation depends on a second highly conserved domain in MYCs amino-terminus ("MYC box II"), we propose that both domains co-operate to transfer elongation factors onto paused RNAPII. ChIP-Seq experiments for MYC-HA (HA-IP) and RNAPII (total,Ser2p,Ser5p) performed in IMEC primary breast epithelial cells. Input-samples were sequenced as controls. The following antibodies were used: HA (Abcam; ab 9110)/ total RNAPII (Santa Cruz; sc-899x)/ Ser2p RNAPII (Abcam; ab 5095)/ Ser5p RNAPII (Covance; MMS-128P)
Project description:The MYC transcription factor is an unstable protein and its turnover is controlled by the ubiquitin system. Ubiquitination enhances MYC-dependent transactivation, but the underlying mechanism remains unresolved. Here we show that proteasomal turnover of MYC is dispensable for recruitment of RNA polymerase II (RNAPII), but is required to promote transcriptional elongation at MYC target genes. Degradation of MYC stimulates histone acetylation and recruitment of BRD4 and P-TEFb to target promoters, leading to phosphorylation of RNAPII CTD and the release of elongating RNAPII. In the absence of degradation, the RNA polymerase II-associated factor (PAF) complex associates with MYC via interaction of its CDC73 subunit with a conserved domain in the amino-terminus of MYC ("MYC box I"), suggesting that a MYC/PAF complex is an intermediate in transcriptional activation. Since histone acetylation depends on a second highly conserved domain in MYCs amino-terminus ("MYC box II"), we propose that both domains co-operate to transfer elongation factors onto paused RNAPII. RNA-Seq Experiments were performed in a primary breast epithelial cell line (IMEC).The cell line expressed doxycycline-inducible versions of MYC (WT;Kless,Swap=WTN-KC). Where indicated cells were transfected with siRNAs (siCtrl;siSKP2). Where indicated cells were treaed with the proteasome inhibitor MG132 or EtOH as solvent control. DGE was performed by comparing Dox-treated populations expressing either Dox-inducible MYC or a vector control or comparing Dox-induced cells with EtOH (solvent control) treated cells.
Project description:The expression of chromatin modifying enzymes needs to be tightly controlled to ensure proper distribution of chromatin modifications. H3 lysine 4 trimethylation (H3K4me3) is a conserved histone modification catalyzed by histone methyltransferase Set1 and its dysregulation is associated with pathologies. Here, we show that Set1 is intrinsically unstable and its protein levels are strictly controlled by ubiquitin-dependent proteasomal degradation within the cell cycle and during gene transcription. Specifically, Set1 contains a destruction box (D-box) that can be recognized by the E3 ligase APC/CCdh1 complex and degraded by the ubiquitin-proteasome pathway. Cla4 phosphorylates serine 228 (S228) within Set1 D-box, which inhibits APC/CCdh1-mediated Set1 proteolysis. During gene transcription, the RNA polymerase II-associated PAF complex facilitates Cla4 to phosphorylate Set1-S228 and protect the chromatin-bound Set1 from degradation. By modulating the stability of Set1, Cla4 and the APC/CCdh1 complex control H3K4me3 levels, which then regulates gene transcription, cell cycle progression and chronological aging. In addition to Set1, there are 141 proteins containing the D-box that can be potentially phosphorylated by Cla4 to prevent their degradation by the APC/CCdh1 complex. Thus, we not only addressed the long-standing question about how Set1 stability is controlled, but also uncovered a new mechanism to regulate protein stability
Project description:The regulation of gene expression by RNA polymerase II (Pol II) is a multistep process requiring the concerted action of diverse transcription factors. Very little is known about in vivo function of transcription factor SPT5 as its deletion results in loss of viability. To circumvent this issue and define in vivo mechanism of action for SPT5, we employed acute degradation of SPT5 and studied its consequence on transcription. We find that SPT5 loss triggers degradation of the core Pol II subunit RPB1, a process which we show to be evolutionarily conserved from yeast to human. This RPB1 degradation requires the E3 ubiquitin ligase Cullin 3, the unfoldase VCP/p97 and a novel form of CDK9 kinase complex. SPT5 specifically stabilizes Pol II at promoter proximal regions, permitting Pol II release from promoters to gene bodies. Our findings provide mechanistic insight into the in vivo function of SPT5 in stabilization of promoter-proximal Pol II prior to release into gene bodies for safeguarding accurate gene expression.
Project description:During transcription, nucleosomes are evicted from regulatory and coding regions yet chromatin structure is stable. Restoration of chromatin structure involves concerted action of chromatin modifying activities. Our analysis demonstrates a genome wide function of the INO80 remodeling complex for stable repositioning of the nucleosome immediately proximal to the transcription initiation site. INO80 dependent remodeling of the promoter proximal nucleosomes has a global repressive role. Recruitment of INO80 to proximal nucleosomes overlaps with the elongating Polymerase II complex assembly. The amount of associated Polymerase II at start sites correlates with INO80 recruitment for inducible and constantly transcribed genes. Furthermore, at highly inducible promoters INO80 is required for repression of bidirectional transcription. Therefore, we suggest a function for INO80 after transcription initiation to achieve Polymerase II dependent reassembly of promoter proximal nucleosomes.
Project description:In Saccharomyces cerevisiae short non-coding RNA (ncRNA) generated by RNA Polymerase II (Pol II) are terminated by the NRD complex consisting of Nrd1, Nab3 and Sen1. We now show that Pcf11, a component of the cleavage and polyadenylation complex (CPAC), is generally required for NRD-dependent transcription termination through the action of its CTD interacting domain (CID). Pcf11 localizes downstream of Nrd1 on NRD terminators, and its recruitment depends on Nrd1. Furthermore mutation of the Pcf11 CID results in Nrd1 retention on chromatin, delayed degradation of ncRNA and restricts Pol II CTD Ser2 phosphorylation and Sen1-Pol II interaction. Finally, the pcf11-13 and sen1-1 mutant phenotypes are very similar as both accumulate RNA:DNA hybrids and display Pol II pausing downstream of NRD terminators. We predict a mechanism whereby Nrd1 and Pcf11 exchange on chromatin facilitates Pol II pausing and CTD Ser2-P phosphorylation. This in turn promotes Sen1 activity that is required for NRD-dependent transcription termination in vivo.
Project description:In Saccharomyces cerevisiae short non-coding RNA (ncRNA) generated by RNA Polymerase II (Pol II) are terminated by the NRD complex consisting of Nrd1, Nab3 and Sen1. We now show that Pcf11, a component of the cleavage and polyadenylation complex (CPAC), is generally required for NRD-dependent transcription termination through the action of its CTD interacting domain (CID). Pcf11 localizes downstream of Nrd1 on NRD terminators, and its recruitment depends on Nrd1. Furthermore mutation of the Pcf11 CID results in Nrd1 retention on chromatin, delayed degradation of ncRNA and restricts Pol II CTD Ser2 phosphorylation and Sen1-Pol II interaction. Finally, the pcf11-13 and sen1-1 mutant phenotypes are very similar as both accumulate RNA:DNA hybrids and display Pol II pausing downstream of NRD terminators. We predict a mechanism whereby Nrd1 and Pcf11 exchange on chromatin facilitates Pol II pausing and CTD Ser2-P phosphorylation. This in turn promotes Sen1 activity that is required for NRD-dependent transcription termination in vivo. ChIP-seq with antibody against pol II in wild type and Pcf11 mutants: Pcf11-2, Pcf11-9 and Pcf11-13 grown at 25C and 37C along with input samples
Project description:Eukaryotic cells package their genomes around histone octamers. In response to DNA damage checkpoint kinase-induced core histone degradation leads to a 20-40% reduction in nucleosome density in yeast. To gain insights into this process we report the first comprehensive proteomic analysis of yeast chromatin and the alterations that occur in response to DNA damage. We analyzed the protein content of formaldehyde cross-linked chromatin using tandem mass tag (TMT), multiplexing and high-resolution mass spectrometry (MS), after sucrose gradient enrichment of the chromatin fraction. Quantitative damage-induced changes in the chromatin-bound proteome (called chromatome), were compared among wild-type cells and those defective for the INO80 remodeler (arp8Δ), or high mobility group box proteins (Nhp6a and Nhp6b, nhp6ΔΔ). We find massive changes in the chromatome in response to Zeocin, which are strongly attenuated in cells lacking a functional INO80 remodeler.