Structures of the mumps virus polymerase complex via cryo-electron microscopy

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• The viral polymerase complex (L-P) is essential for non-segmented negative-strand RNA virus (nsNSV) RNA replication and transcription.
• The precise structures of L-P complexes and their functional implications remain largely unknown.

Purpose of the Study:

• To resolve the structures of the mumps virus (MuV) L-P complex.
• To correlate distinct L-P conformations with viral RNA replication and transcription processes.

Main Methods:

• Cryogenic-electron microscopy (cryo-EM) was used to determine the structures of the MuV L-P complex.
• Comparative analysis with other nsNSV polymerase structures.

Main Results:

• Two distinct conformations of the MuV L-P complex were resolved.
• One conformation features a continuous RNA tunnel to the methyltransferase domain, suggesting a transcription state.
• The phosphoprotein (P) forms parallel tetramers around the large protein (L), with diverse origins of the P's L-binding X domain.

Conclusions:

• The study links specific L-P complex structures to nsNSV genome replication and transcription.
• A sliding model for polymerase complex movement along RNA templates is proposed.