Genome-wide prediction and analysis of yeast RNase III-dependent snoRNA processing signals
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ABSTRACT: In Saccharomyces cerevisiae, the maturation of both pre-rRNA and pre-small nucleolar RNAs (pre-snoRNAs) involves common factors, thereby providing a potential mechanism for the coregulation of snoRNA and rRNA synthesis. In this study, we examined the global impact of the double-stranded-RNA-specific RNase Rnt1p, which is required for pre-rRNA processing, on the maturation of all known snoRNAs. In silico searches for Rnt1p cleavage signals, and genome-wide analysis of the Rnt1p-dependent expression profile, identified seven new Rnt1p substrates. Interestingly, two of the newly identified Rnt1p-dependent snoRNAs, snR39 and snR59, are located in the introns of the ribosomal protein genes RPL7A and RPL7B. In vitro and in vivo experiments indicated that snR39 is normally processed from the lariat of RPL7A, suggesting that the expressions of RPL7A and snR39 are linked. In contrast, snR59 is produced by a direct cleavage of the RPL7B pre-mRNA, indicating that a single pre-mRNA transcript cannot be spliced to produce a mature RPL7B mRNA and processed by Rnt1p to produce a mature snR59 simultaneously. The results presented here reveal a new role of yeast RNase III in the processing of intron-encoded snoRNAs that permits independent regulation of the host mRNA and its associated snoRNA. RNA from wild type, rnt1d and rnt1ts grown at 26 C and 37 C on rich media
Project description:In Saccharomyces cerevisiae, the maturation of both pre-rRNA and pre-small nucleolar RNAs (pre-snoRNAs) involves common factors, thereby providing a potential mechanism for the coregulation of snoRNA and rRNA synthesis. In this study, we examined the global impact of the double-stranded-RNA-specific RNase Rnt1p, which is required for pre-rRNA processing, on the maturation of all known snoRNAs. In silico searches for Rnt1p cleavage signals, and genome-wide analysis of the Rnt1p-dependent expression profile, identified seven new Rnt1p substrates. Interestingly, two of the newly identified Rnt1p-dependent snoRNAs, snR39 and snR59, are located in the introns of the ribosomal protein genes RPL7A and RPL7B. In vitro and in vivo experiments indicated that snR39 is normally processed from the lariat of RPL7A, suggesting that the expressions of RPL7A and snR39 are linked. In contrast, snR59 is produced by a direct cleavage of the RPL7B pre-mRNA, indicating that a single pre-mRNA transcript cannot be spliced to produce a mature RPL7B mRNA and processed by Rnt1p to produce a mature snR59 simultaneously. The results presented here reveal a new role of yeast RNase III in the processing of intron-encoded snoRNAs that permits independent regulation of the host mRNA and its associated snoRNA.
Project description:The paired-end next-generation sequencing of all small RNAs of less than 200 nucleotides in length from four different human cell lines (SKOV3ip1, MCF-7, BJ-Tielf, INOF) allowed us to determine the exact sequence(s) and variations of human box C/D snoRNAs (small nucleolar RNAs), revealing processing patterns of this class of molecules. Two distinct groups of box C/D snoRNAs were identified based on the position of their ends with respect to their characteristic boxes and the terminal base pairing potential. Short box C/D snoRNAs start sharply 4 or 5 nucleotides upstream of their box C and end 2 or 3 nucleotides downstream of their box D. In contrast, long box C/D snoRNAs start 5 or 6 nucleotides upstream of their box C and end 4 or 5 nucleotides downstream of their box D, increasing the likelihood of formation of a k-turn between their boxes C and D. Sequencing of SKOV3ip1 cells following the depletions of NOP58, a core box C/D snoRNA-binding protein and of RBFOX2, a splicing factor, shows that the short box C/D snoRNA forms are significantly more affected by the depletion of RBFOX2 while the long snoRNA forms, which display more canonical box C/D snoRNA features, are significantly more affected by the depletion of NOP58. Together the data suggest that box C/D snoRNAs are divided into at least two groups of RNA with distinct maturation and functional preferences. Small RNAs (<200 nucleotides) were isolated from different human cell lines that were either untreated or depleted of NOP58 or RBFOX2 using specific siRNAs. The resulting libraries were multiplexed and paired-end sequenced using Illumina HiSeq.
Project description:SIRT7 is an NAD+-dependent protein deacetylase with important roles in ribosome biogenesis and cell proliferation. Previous studies have established that SIRT7 is associated with RNA polymerase I, interacts with pre-rRNA and promotes rRNA synthesis. Here we show that SIRT7 is also associated with snoRNAs that are involved in pre-rRNA processing and rRNA maturation. Knockdown of SIRT7 impairs U3 snoRNA-dependent early cleavage steps that are necessary for generation of 18S rRNA. Mechanistically, SIRT7 deacetylates U3-55k, a core component of the U3 snoRNP complex, and reversible acetylation of U3-55k modulates the association of U3-55k with U3 snoRNA. Deacetylation by SIRT7 enhances U3-55k binding to U3 snoRNA, which is a prerequisite for pre-rRNA processing. Under stress conditions, SIRT7 is released from nucleoli, leading to hyperacetylation of U3-55k and attenuation of prerRNA processing. The results reveal a multifaceted role of SIRT7 in ribosome biogenesis, regulating both transcription and processing of rRNA. CLIP-seq was performed in Flag-SIRT7-293T cells.
Project description:The tumour suppressor p14/19ARF regulates ribosomal RNA (rRNA) synthesis by controlling the nucleolar localization of Transcription Termination Factor 1 (TTF1). However, the role played by TTF1 in regulating the rRNA genes and in potentially controlling growth has remained unclear. We now show that TTF1 expression regulates cell growth by determining the cellular complement of ribosomes. Unexpectedly, it achieves this by acting as a “roadblock” to synthesis of the non-coding LncRNA and pRNA that we show are generated from the “Spacer Promoter” duplications present upstream of the 47S pre-rRNA promoter on the mouse and human ribosomal RNA genes. Unexpectedly, the endogenous generation of these non-coding RNAs does not induce CpG methylation or gene silencing. Rather, it acts in cis to suppress 47S preinitiation complex formation and hence de novo pre-rRNA synthesis by a mechanism reminiscent of promoter interference or occlusion. Taken together, our data delineate a pathway from p19ARF to cell growth suppression via the regulation of ribosome biogenesis by non-coding RNAs and validate a key cellular growth law in mammalian cells.
Project description:The tumour suppressor p14/19ARF regulates ribosomal RNA (rRNA) synthesis by controlling the nucleolar localization of Transcription Termination Factor 1 (TTF1). However, the role played by TTF1 in regulating the rRNA genes and in potentially controlling growth has remained unclear. We now show that TTF1 expression regulates cell growth by determining the cellular complement of ribosomes. Unexpectedly, it achieves this by acting as a “roadblock” to synthesis of the non-coding LncRNA and pRNA that we show are generated from the “Spacer Promoter” duplications present upstream of the 47S pre-rRNA promoter on the mouse and human ribosomal RNA genes. Unexpectedly, the endogenous generation of these non-coding RNAs does not induce CpG methylation or gene silencing. Rather, it acts in cis to suppress 47S preinitiation complex formation and hence de novo pre-rRNA synthesis by a mechanism reminiscent of promoter interference or occlusion. Taken together, our data delineate a pathway from p19ARF to cell growth suppression via the regulation of ribosome biogenesis by non-coding RNAs and validate a key cellular growth law in mammalian cells.
Project description:SIRT7 is an NAD+-dependent protein deacetylase with important roles in ribosome biogenesis and cell proliferation. Previous studies have established that SIRT7 is associated with RNA polymerase I, interacts with pre-rRNA and promotes rRNA synthesis. Here we show that SIRT7 is also associated with snoRNAs that are involved in pre-rRNA processing and rRNA maturation. Knockdown of SIRT7 impairs U3 snoRNA-dependent early cleavage steps that are necessary for generation of 18S rRNA. Mechanistically, SIRT7 deacetylates U3-55k, a core component of the U3 snoRNP complex, and reversible acetylation of U3-55k modulates the association of U3-55k with U3 snoRNA. Deacetylation by SIRT7 enhances U3-55k binding to U3 snoRNA, which is a prerequisite for pre-rRNA processing. Under stress conditions, SIRT7 is released from nucleoli, leading to hyperacetylation of U3-55k and attenuation of prerRNA processing. The results reveal a multifaceted role of SIRT7 in ribosome biogenesis, regulating both transcription and processing of rRNA.
Project description:H/ACA small nucleolar RNAs (snoRNAs) guide pseudouridylation as part of a small nucleolar ribonucleoprotein complex (snoRNP). Disruption of H/ACA snoRNA expression in stem cells impairs pluripotency, yet it remains unclear how H/ACA snoRNAs contribute to differentiation. To determine if H/ACA snoRNA expression is dynamic during differentiation, we comprehensively profiled H/ACA snoRNA expression in multiple murine cell types and during differentiation in three cellular models, including mouse embryonic stem cells and mouse myoblasts. We determined that H/ACA snoRNA expression is cell-type specific, and we identified a subset of snoRNAs that are specifically regulated during differentiation. Additionally, we demonstrated that a decrease in Snora27 expression upon differentiation corresponds to a decrease in pseudouridylation of its target site within the E-site transfer RNA (tRNA) binding region of the 28S ribosomal RNA (rRNA) in the large ribosomal subunit. Many of the snoRNAs regulated during differentiation have target nucleotides in the 28S rRNA, and we found that pre-rRNA processing of large subunit precursors is altered during differentiation. Together, these data suggest a model in which H/ACA snoRNAs are specifically regulated during differentiation to potentially alter pseudouridylation and fine tune ribosome function.
Project description:H/ACA small nucleolar RNAs (snoRNAs) guide pseudouridylation as part of a small nucleolar ribonucleoprotein complex (snoRNP). Disruption of H/ACA snoRNA expression in stem cells impairs pluripotency, yet it remains unclear how H/ACA snoRNAs contribute to differentiation. To determine if H/ACA snoRNA expression is dynamic during differentiation, we comprehensively profiled H/ACA snoRNA expression in multiple murine cell types and during differentiation in three cellular models, including mouse embryonic stem cells and mouse myoblasts. We determined that H/ACA snoRNA expression is cell-type specific, and we identified a subset of snoRNAs that are specifically regulated during differentiation. Additionally, we demonstrated that a decrease in Snora27 expression upon differentiation corresponds to a decrease in pseudouridylation of its target site within the E-site transfer RNA (tRNA) binding region of the 28S ribosomal RNA (rRNA) in the large ribosomal subunit. Many of the snoRNAs regulated during differentiation have target nucleotides in the 28S rRNA, and we found that pre-rRNA processing of large subunit precursors is altered during differentiation. Together, these data suggest a model in which H/ACA snoRNAs are specifically regulated during differentiation to potentially alter pseudouridylation and fine tune ribosome function.
Project description:H/ACA small nucleolar RNAs (snoRNAs) guide pseudouridylation as part of a small nucleolar ribonucleoprotein complex (snoRNP). Disruption of H/ACA snoRNA expression in stem cells impairs pluripotency, yet it remains unclear how H/ACA snoRNAs contribute to differentiation. To determine if H/ACA snoRNA expression is dynamic during differentiation, we comprehensively profiled H/ACA snoRNA expression in multiple murine cell types and during differentiation in three cellular models, including mouse embryonic stem cells and mouse myoblasts. We determined that H/ACA snoRNA expression is cell-type specific, and we identified a subset of snoRNAs that are specifically regulated during differentiation. Additionally, we demonstrated that a decrease in Snora27 expression upon differentiation corresponds to a decrease in pseudouridylation of its target site within the E-site transfer RNA (tRNA) binding region of the 28S ribosomal RNA (rRNA) in the large ribosomal subunit. Many of the snoRNAs regulated during differentiation have target nucleotides in the 28S rRNA, and we found that pre-rRNA processing of large subunit precursors is altered during differentiation. Together, these data suggest a model in which H/ACA snoRNAs are specifically regulated during differentiation to potentially alter pseudouridylation and fine tune ribosome function.
Project description:We performed ChIP seq experiment in MDA-MB-134 cell line in order to map the estrogen receptor alpha (ER) binding sites following the estrogen treatment in an ILC model. We have characterized the genome wide recruit of ER and scaned the binding sites for the presence of cofactor motifs. The binding peaks were also correlated to E2 regulated genes in this ILC model. Four samples were subjected to high throughput sequencing: E-ER (estrogen treated followed by ER IP), E-IgG (estrogen treated followed by IgG), V-ER (EtOH treated followed by ER IP) and Input (MCF7 genomic DNA)