ABSTRACT: A mass spectrometry-based proteomic analysis of the Rix1 60S biogenesis complex
through immunoprecipitation of endogenous PELP1 from HEK293T cells.
Project description:The Drosha-DGCR8 complex (Microprocessor) is required for microRNA (miRNA) biogenesis. DGCR8 contains two double-stranded RNA binding motifs that recognize the RNA substrate, whereas Drosha functions as the endonuclease. We have used high-throughput sequencing of RNAs isolated by crosslinking immunoprecipitation (HITS-CLIP) to identify endogenous RNA targets of DGCR8 in mammalian cells. Unexpectedly, miRNAs were not the most abundant targets. DGCR8-bound RNAs comprised several hundred mRNAs as well as snoRNAs and long non-coding RNAs. We found that DGCR8 together with Drosha controls the abundance of several mRNAs, as well as long non-coding RNAs, such as MALAT-1. By contrast, the DGCR8-mediated cleavage of snoRNAs is independent of Drosha, suggesting the involvement of DGCR8 in cellular complexes with other endonucleases. Interestingly, binding of DGCR8 to cassette exons, acts as a novel mechanism to regulate the relative abundance of alternatively spliced isoforms. Collectively, these data provide new insights in the complex role of DGCR8 in controlling the fate of several classes of RNAs. Comparison of RNAs associated to both endogenous (D8) and overexpressed (T7) DGCR8 in HEK293T cells
Project description:The budding yeast E3 SUMO ligase Mms21, a component of the Smc5-6 complex, regulates sister chromatid cohesion, DNA replication, and DNA repair. We identify a role for Mms21 in ribosome biogenesis. The mms21RINGD mutant exhibits reduced rRNA production, nuclear accumulation of 60S and 40S ribosomal proteins, and elevated Gcn4 translation. Genes involved in ribosome biogenesis and translation are down-regulated in the mms21RINGD mutant. Examining gene expression profile of mms21RINGD mutant compared to wild-type by RNA Seq using Ilumina sequencing
Project description:The budding yeast E3 SUMO ligase Mms21, a component of the Smc5-6 complex, regulates sister chromatid cohesion, DNA replication, and DNA repair. We identify a role for Mms21 in ribosome biogenesis. The mms21RINGD mutant exhibits reduced rRNA production, nuclear accumulation of 60S and 40S ribosomal proteins, and elevated Gcn4 translation. Genes involved in ribosome biogenesis and translation are down-regulated in the mms21RINGD mutant.
Project description:Assembly of eukaryotic ribosomes begins in the nucleolus, a compartmentalized membraneless organelle. Although the two ribosomal subunits, 40S and 60S, assemble independently, it remains unknown if these particles are physically sorted as they assemble and how they partition from the central chromatin compartment into the outer nucleolar regions, where maturation occurs. In this study, we show that nucleophosmin specifically mediates the assembly of nascent 60S subunits and that this specificity is determined by its chromatin localization at the rDNA sites encoding for 60S subunit rRNA. Nucleophosmin dissociates from chromatin to bind nascent 60S subunits, causing their partitioning away from chromatin and from nascent 40S subunits through liquid-liquid phase separation. This directs translocation of nascent 60S subunits towards the nucleophosmin-rich granular component, where biogenesis continues. Notably, this compartmentalization increases the efficiency of 60S subunit assembly, specifically the incorporation of the 60S domain III. Our data reveal that the chromatin localization of nucleophosmin determines its specificity in sorting and coordinates the movement of ribosomal subunits into specialized assembly compartments.
Project description:RIME/ChIP-MS analysis for Nucleoporin, Nup214 and CRM1. Rapid Immunoprecipitation Mass spectrometry of Endogenous proteins was used.
Project description:The SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) plays indispensable roles for many physiological processes in a substrate-specific manner; however, the nature of endogenous substrates remains largely elusive. Here we have developed a unique proteomics strategy based on the intrinsic property of the SEL1L-HRD1 ERAD complex to identify potential endogenous ERAD substrates in human kidney cell line HEK293T and mouse brown adipocytes. Over 100 potential substrates involved in many cellular processes, including both membrane and luminal proteins regardless of their glycosylation and disulfide bond status, are identified in each cell type, among which 34 are shared. We further uncover SEL1L-HRD1 ERAD as a suppressor of the biogenesis of glycosylphosphatidylinositol (GPI)-anchored proteins via degrading a key subunit of the GPI-transamidase complex known as phosphatidylinositol glycan anchor biosynthesis class K protein (PIGK). Lastly, several PIGK disease variants are highly unstable and quickly degraded by SEL1L-HRD1 ERAD. This study shows the most effective way to identify cell type-specific proteome-wide potential endogenous SEL1L-HRD1 substrates, and uncovers a new function of SEL1L-HRD1 ERAD in the biogenesis and disease pathogenesis associated with GPI-anchored proteins
Project description:The SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) plays indispensable roles for many physiological processes in a substrate-specific manner; however, the nature of endogenous substrates remains largely elusive. Here we have developed a unique proteomics strategy based on the intrinsic property of the SEL1L-HRD1 ERAD complex to identify potential endogenous ERAD substrates in human kidney cell line HEK293T and mouse brown adipocytes. Over 100 potential substrates involved in many cellular processes, including both membrane and luminal proteins regardless of their glycosylation and disulfide bond status, are identified in each cell type, among which 34 are shared. We further uncover SEL1L-HRD1 ERAD as a suppressor of the biogenesis of glycosylphosphatidylinositol (GPI)-anchored proteins via degrading a key subunit of the GPI-transamidase complex known as phosphatidylinositol glycan anchor biosynthesis class K protein (PIGK). Lastly, several PIGK disease variants are highly unstable and quickly degraded by SEL1L-HRD1 ERAD. This study shows the most effective way to identify cell type-specific proteome-wide potential endogenous SEL1L-HRD1 substrates, and uncovers a new function of SEL1L-HRD1 ERAD in the biogenesis and disease pathogenesis associated with GPI-anchored proteins
Project description:Breast cancer is the most frequently diagnosed malignant neoplasm and the second leading cause of cancer death among women. Epithelial-to-mesenchymal Transition (EMT) plays a critical role in the organism development, providing cell migration and tissue formation. However, its erroneous activation in malignancies can serve as the basis for the dissemination of cancer cells and metastasis. The Zeb1 transcription factor, which regulates the EMT activation, has been shown to play an essential role in malignant transformation. This factor is involved in many signaling pathways that influence a wide range of cellular functions via interacting with many proteins that affect its transcriptional functions. Importantly, the interactome of Zeb1 depends on the cellular context. Here, using the inducible expression of Zeb1 in epithelial breast cancer cells, we identified a substantial list of novel potential Zeb1 interaction partners, including proteins involved in the formation of malignant neoplasms, such as ATP-dependent RNA helicase DDX17and a component of the NURD repressor complex, CTBP2. We confirmed the presence of the selected interactors by immunoblotting with specific antibodies. Further, we demonstrated that co-expression of Zeb1 and CTBP2 in breast cancer patients correlated with the poor survival prognosis, thus signifying the functionality of the Zeb1-CTBP2 interaction.