Writer's block: preventing m 6 A mRNA methylation promotes T cell naivety

N6-methyladenosine (m6A) is a conserved internal modification prevalent in eukaryotic nuclear RNA and determines stem cell fates by influencing mRNA metabolism, especially mRNA stability.1 The m6A modification is imprinted by a ‘writer’ multicomponent N6-adenosine methyltransferase (MT) complex composed of METTL3 and METTL14.2 These two proteins form a stable heterodimer to catalyse M6 mRNA methylation. In their recent paper in Nature, Li et al.3 demonstrate that ablating the MT complex prevents m6A modification and leads to a dramatic alteration of lymphocyte homeostasis where T cells are kept in a naive state.