H/ACA small nucleolar ribonucleoprotein complex (H/ACA snoRNP complex)

Function

• catalyzes pseudouridylation of rRNA
  • this involves the isomerization of uridine such that the ribose is subsequently attached to C5, instead of the normal N1
  • each rRNA can contain up to 100 pseudouridine residues, which may serve to stabilize the conformation of rRNAs
• binds a box H/ACA small nucleolar RNA (snoRNA), which may target the specific site of modification within the RNA substrate
• interacts with TERC, which contains a 3'-terminal domain related to the box H/ACA snoRNAs
• specific interactions with snoRNAs or TERC are mediated by NOLA1 & NOLA2
• H/ACA snoRNPs interact with the SMN complex
  • this is mediated by interaction between GAR1 & SMN1 or SMN2
  • SMN complex may be required for correct assembly of the H/ACA snoRNP complex
• complex contains a stable core formed by binding of 1 or 2 NOLA3-DKC1 heterodimers to NOLA2
• NOLA1 subsequently binds to this core via DKC1

Structure

• subunits: NOLA1, NOLA2, NOLA3, DKC1 (NOLA4)
• DKC1 is presumed to be the catalytic subunit

More general terms

• molecular complex