A functional interaction between the survival motor neuron complex and RNA polymerase II

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The survival motor neuron (SMN) protein, linked to spinal muscular atrophy (SMA), is vital for assembling small nuclear ribonucleoproteins (snRNPs) and spliceosomes.
• RNA helicase A (RHA) is a DEAH box RNA helicase involved in transcription and binds RNA polymerase II (pol II).

Purpose of the Study:

• To investigate the physical and functional association between the SMN complex and RNA polymerase II (pol II).
• To elucidate the role of RNA helicase A (RHA) in mediating the SMN-pol II interaction.

Main Methods:

• Nanoelectrospray mass spectrometry to identify SMN complex-associated proteins.
• In vitro binding assays to assess SMN-RHA interactions.
• Coimmunoprecipitation to detect in vivo associations of SMN complex, pol II, snRNPs, and RHA.
• Cell transfection with a dominant-negative SMN mutant (SMNDeltaN27) to observe effects on nuclear structures and transcription.

Main Results:

• RNA helicase A (RHA) was identified as an SMN complex-associated protein.
• SMN interacts with RHA in vitro, an interaction impaired in SMA-associated SMN mutants.
• The SMN complex associates with pol II, snRNPs, and RHA in vivo, with RHA mediating the SMN-pol II interaction.
• Expression of SMNDeltaN27 led to the accumulation of pol II, snRNPs, and RHA in nuclear structures and inhibited RNA pol I and pol II transcription.

Conclusions:

• The SMN complex exhibits a functional and physical association with pol II.
• The SMN complex plays a role in the assembly of the pol II transcription/processing machinery.
• Dysfunction of the SMN complex, as seen in SMA, may impair transcription through disrupted assembly of the pol II machinery.