Pwp2 mediates UTP-B assembly via two structurally independent domains

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The small subunit (SSU) processome is a large ribonucleoprotein complex essential for early ribosome biogenesis.
• UTP-B is an early-associating multi-subunit protein complex that forms part of the SSU processome.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the hierarchical assembly of the SSU processome.
• To investigate the structural and functional roles of the UTP-B subunit Pwp2p.

Main Methods:

• Structural analysis of Pwp2p.
• Functional analysis of Pwp2p and its domains.
• Investigating protein-protein interactions within the UTP-B complex.
• Assessing the association of UTP-B with pre-ribosomal RNA.

Main Results:

• Pwp2p is essential for the correct assembly of the UTP-B complex.
• Pwp2p mediates the productive association of UTP-B with pre-ribosomal RNA.
• The N-terminal tandem WD-repeat (tWD) domain of Pwp2p interacts with Utp21p, Utp18p, and Utp6p, forming a core complex.
• The C-terminal domains (CTDs) of Pwp2p and Utp21p facilitate the assembly of the Utp12p:Utp13p heterodimer, crucial for UTP-B incorporation into the SSU processome.
• Evidence suggests UTP-B acts as a platform for assembly factors during 20S rRNA precursor maturation.

Conclusions:

• Pwp2p plays a dual role in UTP-B assembly and pre-rRNA binding, mediated by distinct structural domains.
• The structural organization of Pwp2p is critical for the hierarchical assembly of the SSU processome.
• UTP-B may serve as a scaffold for assembly factors in ribosome biogenesis.