A novel adenovirus 19K/IX protein enhances infection by attenuating proteasomal degradation of tyrosine-ubiquitinated capsid protein IX.

The 19K/IX protein enhances human adenovirus type C5 infection by stabilizing capsid protein IX through inhibition of its proteasomal degradation.

• Why it matters: Understanding how adenoviruses regulate their protein stability is crucial for developing therapeutic strategies and improving their use as vectors, yet the mechanisms of capsid protein regulation remain unclear.
• What they did: The study used replication-competent epitope-tagged HAdV-C5 viruses to identify and characterize the 19K/IX transcript, demonstrating its role in binding and stabilizing pIX by preventing its degradation mediated by non-canonical tyrosine ubiquitination.
• The result: This discovery reveals a novel viral regulatory mechanism that enhances infectious particle production and underscores the importance of non-canonical tyrosine ubiquitination in adenovirus protein homeostasis.