Catalyzes the transfer of a dimethylallyl group onto the adenine at position 37 in the anticodon loop on a specific subset of tRNAs both in the cytosol and the mitochondrion, leading to the formation of N6-(dimethylallyl)adenosine (i(6)A). This modification optimizes the codon:anticodon fit in the ribosome and promotes translational fidelity. Competes with the farnesyl pyrophosphate synthase ERG20 for the common substrate dimethylallyl diphosphate (DMAPP). adenosine(37) in tRNA + dimethylallyl diphosphate = diphosphate + N(6)-dimethylallyladenosine(37) in tRNA [MOD+] forms multicytoplasmic aggregates that do not colocalize to either mitochondria or nucleus. The core aggregation region, although lacking the prion-typical Gln/Asn (Q/N)-rich domain, is required for the formation of the amyloid-like fibrillar aggregates. [MOD+] is the prion form of MOD5. [MOD+] is the result of a conformational change of the cellular MOD5 protein that becomes self-propagating and infectious. This conformational change generates a form of MOD5 that assembles into amyloid-like fibrillar aggregates. [MOD+]-aggregates sequester soluble MOD5, resulting in decreased levels of (i(6)A)-modified tRNAs and higher ergosterol levels, due to less competition for ERG20, which uses the same substrate DMAPP than MOD5. [MOD+] can be cured by GdnHCl and by deletion of the molecular chaperone HSP104, which is required for [MOD+] propagation. The [MOD+] state acquires resistance against antifungal agents such as flucanozole, ketoconazole and clotrimazole that inhibit ergosterol biosynthesis. De novo appearance of [MOD+] is favored in the presence of antifungal agents, and the growth advantage of [MOD+] is lost when the cells are released from the selective pressure. Thus, the conformational switch of MOD5 from a soluble state to a prion state allows the cell to adapt to the harmful environment of anti-fungal drugs by up-regulating ergosterol biosynthesis at the expense of tRNA modification. Present with 2020 molecules/cell in log phase SD medium. Belongs to the IPP transferase family.