U3 small nucleolar RNA (SNORD3A (U3))

U3 small nucleolar RNA (SNORD3A, also called U3) is a highly conserved noncoding RNA found in the nucleolus of eukaryotic cells[1][5]. It is a member of the C/D box snoRNA family, but unlike most C/D box snoRNAs, U3 does not guide 2'-O-methylation of ribosomal RNA. Instead, it is essential for early cleavage steps in pre-rRNA processing, acting as a guide for assembling snoRNP complexes involved in the maturation of ribosomal RNA—a critical step for ribosome biogenesis[1][5]. U3 snoRNA achieves its function by forming complexes with specific proteins (fibrillarin/Nop1p, NOP56, NOP58, SNU13/15.5 kD protein)[1][5]. It is localized to the nucleolus and is required for proper processing and assembly of eukaryotic ribosomes[5]. U3 snoRNA is not classified as a receptor, enzyme, or transporter, nor is it a direct drug target. Its disruption can affect cell growth and division due to faulty ribosome synthesis, underlining its fundamental role in cellular physiology. However, its aberrant expression is not currently linked as a primary driver of specific human diseases or as a therapeutic target.

Other names

SNORD3AU3RNU3U3 snoRNA AU3 small nucleolar RNA A

No drugs are known to target SNORD3A/U3, so mechanisms of drug action do not apply.