S-adenosyl-L-methionine-dependent guanine N(1)- methyltransferase that catalyzes the formation of N(1)-methylguanine at position 9 (m1G9) in tRNAs (PubMed:23042678, PubMed:25053765). Probably not able to catalyze formation of N(1)-methyladenine at position 9 (m1A9) in tRNAs (PubMed:23042678). {ECO:0000269|PubMed:23042678, ECO:0000269|PubMed:25053765}. This is the function of Ensembl gene identifier ENSG00000145331 (TRMT10A, tRNA methyltransferase 10A).