Project description:The interactions between proteins and nucleic acids have a fundamental function in many biological processes well beyond nuclear gene transcription and include RNA homeostasis, protein translation and pathogen sensing for innate immunity. While our knowledge of the ensemble of proteins binding individual mRNAs in mammalian cells has greatly been augmented by recent surveys, no systematic study on the native proteins of human cells differentially engaging various types of nucleic acids in a non sequence-specific manner has been reported. We designed an experimental approach to cover the non sequence-specific RNA and DNA binding space broadly, including methylation, and test for its ability to interact with the human proteome. We used 25 rationally designed nucleic acid probes in an affinity purification mass spectrometry and bioinformatics workflow to identify proteins from whole cell extracts of three different human cell lines. The proteins were profiled for their binding preferences to the different general types of nucleic acids. The study identified 746 high confidence direct binders, 249 of which were devoid of previous experimental evidence for binding nucleic acids. We could assign 513 specific affinities for sub-types of nucleic acid probes to 219 distinct proteins and to individual domains. The evolutionary conserved protein YB-1, previously associated with cancer and gene regulation, is shown to bind methylated cytosine preferentially conferring YB-1 a potential epigenetic function. Collectively, the dataset represents a rich resource of experimentally determined nucleic acid-specific binding proteins in humans and, indirectly, for other species. Identification of genomic YB-1 binding sites in HEK293 cells
Project description:The interactions between proteins and nucleic acids have a fundamental function in many biological processes well beyond nuclear gene transcription and include RNA homeostasis, protein translation and pathogen sensing for innate immunity. While our knowledge of the ensemble of proteins binding individual mRNAs in mammalian cells has greatly been augmented by recent surveys, no systematic study on the native proteins of human cells differentially engaging various types of nucleic acids in a non sequence-specific manner has been reported. We designed an experimental approach to cover the non sequence-specific RNA and DNA binding space broadly, including methylation, and test for its ability to interact with the human proteome. We used 25 rationally designed nucleic acid probes in an affinity purification mass spectrometry and bioinformatics workflow to identify proteins from whole cell extracts of three different human cell lines. The proteins were profiled for their binding preferences to the different general types of nucleic acids. The study identified 746 high confidence direct binders, 249 of which were devoid of previous experimental evidence for binding nucleic acids. We could assign 513 specific affinities for sub-types of nucleic acid probes to 219 distinct proteins and to individual domains. The evolutionary conserved protein YB-1, previously associated with cancer and gene regulation, is shown to bind methylated cytosine preferentially conferring YB-1 a potential epigenetic function. Collectively, the dataset represents a rich resource of experimentally determined nucleic acid-specific binding proteins in humans and, indirectly, for other species.
Project description:Organic solvents and Ti4+-IMAC capture of formaldehyde (FA) cross-linked cells followed by mass spectrometry analysis to identify nucleic acid binding proteins in human cells.
Project description:CNBP is a eukaryote-conserved nucleic-acid binding protein required in mammals for embryonic development. It contains seven CCHC-type zinc-finger domains and was suggested to act as a nucleic acid chaperone, as well as a transcription factor. Here, we identify all CNBP isoforms as cytoplasmic messenger RNA (mRNA)-binding proteins. Using Photoactivatable Ribonucleoside Enhanced Cross-linking and Immunoprecipitation, we mapped its binding sites on RNA at nucleotide-level resolution on a genome-wide scale and find that CNBP interacted with 3961 mRNAs in human cell lines, preferentially at a G-rich motif close to the AUG start codon on mature mRNAs. Loss- and gain-of-function analyses coupled with system-wide RNA and protein quantification revealed that CNBP did not affect RNA abundance, but rather promoted translation of its targets. This is consistent with an RNA chaperone function of CNBP helping to resolve secondary structures, thus promoting translation.
Project description:CNBP is a eukaryote-conserved nucleic-acid binding protein required in mammals for embryonic development. It contains seven CCHC-type zinc-finger domains and was suggested to act as a nucleic acid chaperone, as well as a transcription factor. Here, we identify all CNBP isoforms as cytoplasmic messenger RNA (mRNA)-binding proteins. Using Photoactivatable Ribonucleoside Enhanced Cross-linking and Immunoprecipitation, we mapped its binding sites on RNA at nucleotide-level resolution on a genome-wide scale and find that CNBP interacted with 3961 mRNAs in human cell lines, preferentially at a G-rich motif close to the AUG start codon on mature mRNAs. Loss- and gain-of-function analyses coupled with system-wide RNA and protein quantification revealed that CNBP did not affect RNA abundance, but rather promoted translation of its targets. This is consistent with an RNA chaperone function of CNBP helping to resolve secondary structures, thus promoting translation.
Project description:Background: The intracellular pathogen Mycobacterium tuberculosis is known to encounter several stress conditions during infection, including low pH, hypoxia, starvation and oxidative and nitrosative stress. Mycobacterial adaptation to stress conditions is, in part, mediated by several nucleic acid-associated proteins. In this study, we sought to establish an affinity purification-mass spectrometry (AP-MS) approach that would enable the collective identification of nucleic acid-associated proteins in mycobacteria. We hypothesized that targeting the RNA polymerase complex through affinity purification would allow for the identification of RNA- and DNA-associated proteins that not only maintain the bacterial chromosome but also enable transcription and translation. Results: AP-MS analysis of the RNA polymerase β-subunit cross-linked to nucleic acids identified 275 putative nucleic acid-associated proteins in the model organism Mycobacterium smegmatis under standard culturing conditions. The AP-MS approach successfully identified proteins that are known to make up the RNA polymerase complex, as well as several other known RNA polymerase complex-associated proteins such as a DNA polymerase, sigma factors, transcriptional regulators, and helicases. Gene ontology enrichment analysis of the identified proteins revealed that this approach selected for proteins with GO terms associated with nucleic acids and cellular metabolism. Importantly, we identified several proteins of unknown function not previously known to be associated with nucleic acids. Validation of several candidate nucleic acid-associated proteins demonstrated for the first time DNA association of ectopically expressed MSMEG_1060, MSMEG_2695 and MSMEG_4306 through affinity purification. Conclusions: Effective identification of nucleic acid-associated proteins, which make up the RNA polymerase complex as well as other DNA- and RNA-associated proteins, was facilitated by affinity purification of the RNA polymerase β-subunit in M. smegmatis. The successful identification of several transcriptional regulators suggest that our approach could be sensitive enough to investigate the nucleic acid-associated proteins that maintain cellular functions and mediate transcriptional and translational change in response to environmental stress.