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Tetracyclines Modify Translation By Targeting Key Human rRNA Substructures

ABSTRACT: Mortison JD, Schenone M, Myers JA, Zhang Z, Chen L, Ciarlo C, Comer E, Natchiar SK, Carr SA, Klaholz BP, Myers AG. Cell Chem Bio 2018. Apart from their antimicrobial properties, tetracyclines demonstrate clinically validated effects in the amelioration of pathological inflammation and human cancer. Delineation of the target(s) and mechanism(s) responsible for these effects, however, has remained elusive. Here, employing quantitative mass spectrometry-based proteomics, we identified human 80S ribosomes as targets of the tetracyclines Col-3 and doxycycline. We then developed in-cell click selective crosslinking with RNA sequence profiling (icCL-Seq) to map binding sites for these tetracyclines on key human rRNA substructures at nucleotide resolution. Importantly, we found that structurally and phenotypically variant tetracycline analogs could chemically discriminate these rRNA binding sites. We also found that tetracyclines both subtly modify human ribosomal translation and selectively activate the cellular integrated stress response (ISR). Together, the data reveal that targeting of specific rRNA substructures, activation of the ISR, and inhibition of translation are correlated with the anti-proliferative properties of tetracyclines in human cancer cell lines.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Steven A. Carr

PROVIDER: MSV000082819 | MassIVE | Wed Aug 15 09:02:00 BST 2018

REPOSITORIES: MassIVE

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Project description:Eukaryotic ribosomal RNA carries diverse posttranscriptional modifications, among which the evolutionarily conserved 2’-O-methylation (2’-O-Me) occurs at more than 100 sites and is essential for ribosome biogenesis. Plasticity of 2´-O-Me in ribosomes and its functional consequences in human disease are not yet known. Here, we present the full rRNA 2’-O-Me landscape (ribomethylome) of human acute myeloid leukemia (AML) through profiling 94 patient samples as well as 21 normal hematopoietic samples of 5 different lineages. While interior modification sites in functional centers are persistently fully 2’-O-methylated in human AMLs, methylation on ribosome exterior sites is unprecedentedly dynamic. Higher 2’-O-methylation on exterior dynamic sites is associated with leukemia stem cell (LSC) signatures. Forced expression of enzymatically active but not of the catalytic defect 2’-O-methyltransferase FBL induces AML stemness and accelerates leukemogenesis in patient-derived xenografts. Mechanistically, ribomethylome dynamics shifted mRNA ribosome translation preferences. High rRNA 2’-O-Me enhances translation of amino acid transporters enriched in optimal codons and subsequently increases intra-cellular amino acid levels. Methylation on a single exterior modification site affects leukemia stem cell activity. The Guanosine 1447 on the small subunit ribosomal RNA is the most variable site in primary AMLs. Gm1447 is increased in leukemia stem cell populations compared to non-leukemogenic blast cells and AML specimens with higher Gm1447 are enriched for leukemia stem cell genes. Comparison of Gm1447high and Gm1447low ribosome structure solved by cryo-electron microscopy demonstrated disassociation of LYAR from Gm1447low ribosomes. Suppression of Gm1447 alone is sufficient to suppress translation of amino acid transporters, resulting in decreased cellular amino acid levels and leukemia stem cell activity. Taken together, our data reveal the dynamic FBL-mediated rRNA 2'-O-Me landscape as a novel epitranscriptomic level of control employed by leukemic stem cells and may enable new strategies to target human AML.

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Tetracyclines Modify Translation By Targeting Key Human rRNA Substructures

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