Project description:Recognition of modified histones by “reader” proteins plays a critical role in the regulation of transcription1. H3K36 trimethylation (H3K36me3) is deposited onto the nucleosomes in the transcribed regions following RNA polymerase II (Pol II) elongation. In yeast, this mark in turn recruits epigenetic regulators to reset the chromatin at an appropriate state to suppress cryptic transcription2,3. However, much less is known about the role of H3K36me3 in transcription regulation in mammals. This is further complicated by the transcription-coupled incorporation of the histone variant H3.3 in gene bodies4. Here we show that the candidate tumor suppressor ZMYND11 specifically recognizes H3K36me3 on H3.3 (H3.3K36me3) and regulates Pol II elongation. Structural studies reveal that in addition to the trimethyl-lysine binding by an aromatic cage within the PWWP domain, the H3.3-dependent recognition is mediated by the encapsulation of the H3.3-specific “Ser31” residue in a composite pocket formed by the tandem bromo-PWWP domains of ZMYND11. ChIP-sequencing analysis reveal a genome-wide colocalization of ZMYND11 with H3K36me3 and H3.3 in gene bodies, and its occupancy requires the pre-deposition of H3.3K36me3. Although ZMYND11 is associated with highly expressed genes, it functions as an unconventional transcription corepressor via modulating the transition of the promoter-proximal paused Pol II to elongation. ZMYND11 is critical for the repression of a transcriptional program that is essential for tumor cell growth; higher expression of ZMYND11 is observed in triple-negative breast cancer patients with better prognosis. Consistently, overexpression of ZMYND11 suppresses cancer cell growth and tumor formation in mice. Together, this study identifies ZMYND11 as an H3.3-specific reader of H3K36me3 that links the histone variant-mediated transcription elongation control to tumor suppression. ChIP-seq analysis of ZMYND11, H3K36me3 in U2OS cells and ZMYND11 knockdown cells; ChIP-seq of H3.3 in Flag-H3.3 stable U2OS cells; RNA-seq of ZNYMD11 depleted U2OS cells.
Project description:In the process of translation, ribosomes first bind to mRNAs (translation initiation) and then move along the mRNA (elongation) to synthesize proteins. Elongation pausing is deemed highly relevant to co-translational folding of nascent peptides and the functionality of protein products, which positioned the evaluation of elongation speed as one of the central questions in the field of translational control. By employing three types of RNA-seq methods, we experimentally and computationally resolved elongation speed at individual gene level and under physiological condition in human cells. We proposed the elongation velocity index (EVI) as a relative measure and successfully distinguished slow-translating genes from the background translatome. The proteins encoded by the low-EVI genes are more stable than the proteome background. In normal cell and lung cancer cell comparisons, we found that the relatively slow-translating genes are relevant to the maintenance of malignant phenotypes. In addition, we identified cell-specific slow-translating codons, which may serve as a causal factor of elongation deceleration. We sequenced mRNA, translating mRNA (RNC-mRNA) and ribosome footprints in normally growing HeLa cells.
Project description:In the process of translation, ribosomes first bind to mRNAs (translation initiation) and then move along the mRNA (elongation) to synthesize proteins. Elongation pausing is deemed highly relevant to co-translational folding of nascent peptides and the functionality of protein products, which positioned the evaluation of elongation speed as one of the central questions in the field of translational control. By employing three types of RNA-seq methods, we experimentally and computationally resolved elongation speed at individual gene level and under physiological condition in human cells. We proposed the elongation velocity index (EVI) as a relative measure and successfully distinguished slow-translating genes from the background translatome. The proteins encoded by the low-EVI genes are more stable than the proteome background. In normal cell and lung cancer cell comparisons, we found that the relatively slow-translating genes are relevant to the maintenance of malignant phenotypes. In addition, we identified cell-specific slow-translating codons, which may serve as a causal factor of elongation deceleration.
Project description:RNA polymerase II (Pol II) elongation is a critical step in gene expression. Here we find that NDF, which was identified as a bilaterian nucleosome-destabilizing factor, is also a Pol II transcription factor that stimulates elongation with plain DNA templates in the absence of nucleosomes. NDF binds directly to Pol II and enhances elongation by a different mechanism than does transcription factor TFIIS. Moreover, yeast Pdp3, which is related to NDF, binds to Pol II and stimulates elongation. Thus, NDF is a Pol II-binding transcription elongation factor that is localized over gene bodies and is conserved from yeast to humans.
Project description:Ribosome profiling data reports on the distribution of translating ribosomes, at steady-state, with codon-level resolution. We present a robust method to extract codon translation rates and protein synthesis rates from these data, and identify causal features associated with elongation and translation efficiency in physiological conditions in yeast. We show that neither elongation rate nor translational efficiency is improved by experimental manipulation of the abundance or body sequence of the rare AGG tRNA. Deletion of three of the four copies of the heavily used ACA tRNA shows a modest efficiency decrease that could be explained by other rate-reducing signals at gene start. This suggests that correlation between codon bias and efficiency arises as selection for codons to utilize translation machinery efficiently in highly translated genes. We also show a correlation between efficiency and RNA structure calculated both computationally and from recent structure probing data, as well as the Kozak initiation motif, which may comprise a mechanism to regulate initiation. We test whether tRNA abundance affects elongation or translation efficiency by changing the tRNA levels through deletion or over expression and measuring the ribosomal dwell time at each codon using a robust statistical method that accounts for flow conservation.
Project description:We have previously shown that RNA polymerase II (Pol II) pause release and transcriptional elongation involve phosphorylation of the factor TRIM28 by the DNA damage response (DDR) kinases ATM and DNA-PK. Here, we report a significant role for DNA breaks and DDR signaling in the mechanisms of transcriptional elongation in stimulus-inducible genes in humans. Our data show the enrichment of TRIM28 and γH2AX on serum-induced genes and the important function of DNA-PK for Pol II pause release and transcriptional activation-coupled DDR signaling on these genes. γH2AX accumulation decreases when P-TEFb is inhibited, confirming that DDR signaling results from transcriptional elongation. In addition, transcriptional elongation-coupled DDR signaling involves topoisomerase II because inhibiting this enzyme interferes with Pol II pause release and γH2AX accumulation. Our findings propose that DDR signaling is required for effective Pol II pause release and transcriptional elongation through a novel mechanism involving TRIM28, DNA-PK, and topoisomerase II 42 samples in total. IP targets were gammaH2ax, s2-pol-II, pol-II, pTRIM28, DNA-pk, topo-IIB. Experimental conditions included DMSO treatment (control), pTEFb, topoII-i, dnapk-i. Matched non-specific IP samples used for control in peak calling.
Project description:During translation elongation, the ribosome ratchets along its mRNA template, incorporating each new amino acid and translocating from one codon to the next. The elongation cycle requires dramatic structural rearrangements of the ribosome. We show here that deep sequencing of ribosome-protected mRNA fragments reveals not only the position of each ribosome but also, unexpectedly, its particular stage of the elongation cycle. Sequencing reveals two distinct populations of ribosome footprints, 28-30 nucleotides and 20-22 nucleotides long, representing translating ribosomes in distinct states, differentially stabilized by specific elongation inhibitors. We find that the balance of small and large footprints varies by codon and is correlated with translation speed. The ability to visualize conformational changes in the ribosome during elongation, at single-codon resolution, provides a new way to study the detailed kinetics of translation and a new probe with which to identify the factors that affect each step in the elongation cycle. Ribosome profiling, or sequencing of ribosome-protected mRNA fragments, in yeast. We assay ribosome footprint sizes and positions in three conditions: untreated yeast (3 replicates) and yeast treated with translation inhibitors cycloheximide (2 replicates) and anisomycin (2 biological replicates, one technical replicate). We also treat yeast with 3-aminotriazole to measure the effect of limited histidine tRNAs on ribosome footprint size and distribution (two treatment durations).
Project description:Recognition of modified histones by “reader” proteins plays a critical role in the regulation of transcription1. H3K36 trimethylation (H3K36me3) is deposited onto the nucleosomes in the transcribed regions following RNA polymerase II (Pol II) elongation. In yeast, this mark in turn recruits epigenetic regulators to reset the chromatin at an appropriate state to suppress cryptic transcription2,3. However, much less is known about the role of H3K36me3 in transcription regulation in mammals. This is further complicated by the transcription-coupled incorporation of the histone variant H3.3 in gene bodies4. Here we show that the candidate tumor suppressor ZMYND11 specifically recognizes H3K36me3 on H3.3 (H3.3K36me3) and regulates Pol II elongation. Structural studies reveal that in addition to the trimethyl-lysine binding by an aromatic cage within the PWWP domain, the H3.3-dependent recognition is mediated by the encapsulation of the H3.3-specific “Ser31” residue in a composite pocket formed by the tandem bromo-PWWP domains of ZMYND11. ChIP-sequencing analysis reveal a genome-wide colocalization of ZMYND11 with H3K36me3 and H3.3 in gene bodies, and its occupancy requires the pre-deposition of H3.3K36me3. Although ZMYND11 is associated with highly expressed genes, it functions as an unconventional transcription corepressor via modulating the transition of the promoter-proximal paused Pol II to elongation. ZMYND11 is critical for the repression of a transcriptional program that is essential for tumor cell growth; higher expression of ZMYND11 is observed in triple-negative breast cancer patients with better prognosis. Consistently, overexpression of ZMYND11 suppresses cancer cell growth and tumor formation in mice. Together, this study identifies ZMYND11 as an H3.3-specific reader of H3K36me3 that links the histone variant-mediated transcription elongation control to tumor suppression.
Project description:The ribosome is central to cellular stress responses because it serves as a sensor to activate signaling pathways that determine cell fate. While the activation of these signaling pathways by translation elongation inhibitors has been well characterized, the impact of these inhibitors on mRNA dynamics remains unclear. Here we use TimeLapse sequencing to investigate how translational stress impacts mRNA dynamics in human cells. Our results reveal that a distinct group of transcripts is stabilized in response to the translation elongation inhibitor emetine. These stabilized mRNAs are short-lived at steady state and many of them encode C2H2 zinc finger proteins. The codon compositions of these stabilized transcripts are suboptimal compared to short-lived mRNAs that are not stabilized. Finally, we show that stabilization of these transcripts is independent of the signaling pathways activated by ribosome collisions, as well as of canonical ribosome quality control factors. Our data describe a group of transcripts whose degradation is particularly sensitive to the inhibition of translation elongation.