Catalytic subunit of a heterodimer with TRMT112/C04H5.1, which specifically methylates the 6th position of adenine in position 1717 of 18S rRNA. adenosine in rRNA + S-adenosyl-L-methionine = H(+) + N(6)-methyladenosine in rRNA + S-adenosyl-L-homocysteine Heterodimer; heterodimerizes with TRMT112/C04H5.1. Worms are viable and do not display obvious developmental defects; they however exhibit significantly longer lifespan and heat resistance (PubMed:33357433). Cells show reduced N6-methylation of adenine(1717) in 18S rRNA (PubMed:33357433). Belongs to the methyltransferase superfamily. PrmA family.