18S rRNA (guanine-N7)-methyltransferase (BUD23)

18S rRNA (guanine-N7)-methyltransferase (BUD23) is an *S-adenosyl-L-methionine–dependent* enzyme responsible for introducing a specific N7-methylguanosine mark into 18S rRNA at a conserved residue close to the ribosome's functional core, necessary for proper small subunit assembly and function in eukaryotes[1][5]. Beyond its methyltransferase role, BUD23 acts as a ribosome maturation factor: its presence is required for correct processing of pre-18S rRNA and transition of pre-ribosomal particles from the processome to the pre-40S state, an essential checkpoint in ribosome biogenesis[2][4][5]. BUD23 interacts tightly with the cofactor TRMT112, which is essential for its protein stability and activity[1][3][5]. It is evolutionarily conserved and expressed both in nucleus and cytoplasm, and loss of function severely impairs translation, especially of nuclear-encoded mitochondrial proteins, leading to mitochondrial dysfunction[1]. In humans, BUD23 is also known as WBSCR22, a gene deleted in Williams-Beuren syndrome. Disruption or aberrant expression has been linked to cancer and ribosomopathies; complete loss is embryonic-lethal in mice and causes severe cardiac dysfunction, underlining its critical role in cellular and organismal homeostasis[1].

Other names

MERM1WBSCR22HUSSY-03PP3381MGC19709MGC2022MGC5140WBMTMetastasis-related methyltransferase 1Williams-Beuren syndrome chromosomal region 22 proteinBud site selection protein 23 homologribosome biogenesis methyltransferase WBSCR22HASJ4442HUSSY-3probable 18S rRNA (guanine-N7)-methyltransferaseWilliams-Beuren candidate region putative methyltransferase

Inhibitors would block 18S rRNA methylation at G1639 (human)/G1575 (yeast), disrupt ribosome maturation, and impair translation.