Molecular basis of RNA guanine-7 methyltransferase (RNMT) activation by RAM.
Nucleic Acids Res
; 44(21): 10423-10436, 2016 Dec 01.
Article
em En
| MEDLINE
| ID: mdl-27422871
ABSTRACT
Maturation and translation of mRNA in eukaryotes requires the addition of the 7-methylguanosine cap. In vertebrates, the cap methyltransferase, RNA guanine-7 methyltransferase (RNMT), has an activating subunit, RNMT-Activating Miniprotein (RAM). Here we report the first crystal structure of the human RNMT in complex with the activation domain of RAM. A relatively unstructured and negatively charged RAM binds to a positively charged surface groove on RNMT, distal to the active site. This results in stabilisation of a RNMT lobe structure which co-evolved with RAM and is required for RAM binding. Structure-guided mutagenesis and molecular dynamics simulations reveal that RAM stabilises the structure and positioning of the RNMT lobe and the adjacent α-helix hinge, resulting in optimal positioning of helix A which contacts substrates in the active site. Using biophysical and biochemical approaches, we observe that RAM increases the recruitment of the methyl donor, AdoMet (S-adenosyl methionine), to RNMT. Thus we report the mechanism by which RAM allosterically activates RNMT, allowing it to function as a molecular rheostat for mRNA cap methylation.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Ligação a RNA
/
Metiltransferases
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article