TSR3 ribosome maturation factor (TSR3)

TSR3 ribosome maturation factor (TSR3) is a highly conserved eukaryotic enzyme required for the final maturation steps of 18S rRNA in the cytoplasmic phase of small ribosomal subunit (40S) biogenesis[1][3]. It functions as an aminocarboxypropyltransferase, utilizing S-adenosylmethionine (SAM) as a donor to install a universally conserved chemical modification—N1-methyl-N3-aminocarboxypropyl-pseudouridine (m^1acp^3Ψ)—at a specific site near the P-site of the 18S rRNA[1][3]. This modification is crucial for proper ribosome assembly and ensures the release of fully mature, functionally competent ribosomal subunits[1]. TSR3’s modification activity temporally coordinates the dissociation and binding of other ribosome assembly factors (notably Rio2 and Rio1 kinases), serving as a checkpoint for quality control in ribosome maturation[1]. Loss or inactivation of TSR3 leads to accumulation of immature rRNA precursors and defective ribosomes, affecting protein synthesis and overall cell growth[1][3]. The enzyme is homologous to the SPOUT-class RNA methyltransferases but uniquely transfers an aminocarboxypropyl group rather than a methyl group due to unique features in its SAM binding site[3]. Currently, there are no known drugs that target TSR3, and it is primarily studied as a fundamental factor for ribosome assembly rather than as a therapeutic target.

Other names

18S rRNA aminocarboxypropyltransferaseC16orf42UND313LHsTsr3MGC2438120S rRNA accumulation protein 3 homologprobable ribosome biogenesis protein C16orf42ribosome biogenesis protein TSR3 homolog

Not therapeutically targeted; mechanism is transfer of an aminocarboxypropyl group (from S-adenosylmethionine donor) to pseudouridine in 18S rRNA during ribosome assembly