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Noncatalytic regulation of 18S rRNA methyltransferase DIMT1 in acute myeloid leukemia.

ABSTRACT: Several rRNA-modifying enzymes install rRNA modifications while participating in ribosome assembly. Here, we show that 18S rRNA methyltransferase DIMT1 is essential for acute myeloid leukemia (AML) proliferation through a noncatalytic function. We reveal that targeting a positively charged cleft of DIMT1, remote from the catalytic site, weakens the binding of DIMT1 to rRNA and mislocalizes DIMT1 to the nucleoplasm, in contrast to the primarily nucleolar localization of wild-type DIMT1. Mechanistically, rRNA binding is required for DIMT1 to undergo liquid-liquid phase separation, which explains the distinct nucleoplasm localization of the rRNA binding-deficient DIMT1. Re-expression of wild-type or a catalytically inactive mutant E85A, but not the rRNA binding-deficient DIMT1, supports AML cell proliferation. This study provides a new strategy to target DIMT1-regulated AML proliferation via targeting this essential noncatalytic region.

SUBMITTER: Gonskikh Y

PROVIDER: S-EPMC10153457 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature

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Noncatalytic regulation of 18<i>S</i> rRNA methyltransferase DIMT1 in acute myeloid leukemia.

Gonskikh Yulia Y Stoute Julian J Shen Hui H Budinich Krista K Pingul Bianca B Schultz Kollin K Elashal Heidi H Marmorstein Ronen R Shi Junwei J Liu Kathy Fange KF

Genes & development 20230406 7-8

Several rRNA-modifying enzymes install rRNA modifications while participating in ribosome assembly. Here, we show that 18<i>S</i> rRNA methyltransferase DIMT1 is essential for acute myeloid leukemia (AML) proliferation through a noncatalytic function. We reveal that targeting a positively charged cleft of DIMT1, remote from the catalytic site, weakens the binding of DIMT1 to rRNA and mislocalizes DIMT1 to the nucleoplasm, in contrast to the primarily nucleolar localization of wild-type DIMT1. Me ...[more]

PMID: 37024283

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Project description:Activity of the enzyme thiopurine methyltransferase (TPMT) determines the anti-leukemic effect of thiopurines used in the chemotherapy of acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML). TPMT status and its effects on treatment outcome have been studied extensively in ALL and autoimmune disorders, but few data is available on TPMT in AML. The present study assessed the genetic polymorphisms and activity of TPMT in children with AML at different treatment stages, and compared the results with those obtained for children with ALL. The study included 33 children with AML (0.7-19.7 years) treated with 6-thioguanine (6-TG) according to the AML-BFM 2004 Protocol. Blood samples were collected at diagnosis, during and following maintenance chemotherapy from 8, 10 and 17 patients with AML (the assay was performed at two time points in 2 patients), respectively. Blood samples from 105 children with ALL were obtained at diagnosis, during the maintenance chemotherapy and following the cessation of the chemotherapy from 16, 55 and 34 children, respectively. The activity of TPMT in red blood cells lysates was measured using an enzymatic reaction based on the conversion of 6-mercaptopurine into 6-methylmercaptopurine, involving S-adenozyl-L-methionine as the methyl group donor. TPMT mutations were determined using a polymerase chain reaction/restriction fragment length polymorphism method. Median TPMT activity at diagnosis, during maintenance chemotherapy and following chemotherapy was 43.1, 47,3 and 41.7 nmol 6-mMP g-1 Hb h-1, respectively. All patients with AML exhibited the homozygous TPMT*1/*1 genotype, with the exception of 1, who was a heterozygote with the TPMT*1/*3C genotype and demonstrated a TPMT activity level at diagnosis of 42.5 nmol 6-mMP g-1 Hb h-1. At each chemotherapy stage, the median TPMT activities in children with AML were significantly increased compared with the median TPMT activities in children with ALL. The preliminary results suggest that the TPMT activity in AML may be increased compared with that in ALL. Comprehensive studies on the association between thiopurine metabolism and treatment outcome in AML are required, with regard to the cytogenetic and molecular factors currently used for AML risk stratification.

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.

Dataset Information

Noncatalytic regulation of 18S rRNA methyltransferase DIMT1 in acute myeloid leukemia.

Publications

Noncatalytic regulation of 18<i>S</i> rRNA methyltransferase DIMT1 in acute myeloid leukemia.

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