hCLE/C14orf166, a cellular protein required for viral replication, is incorporated into influenza virus particles

Abstract

The influenza A virus polymerase associates with a number of cellular transcription-related factors, including the RNA polymerase II (RNAP II). We previously described that the cellular protein hCLE/C14orf166 interacts with and stimulates influenza virus polymerase as well as RNAP II activities. Here we show that, despite the considerable cellular shut-off observed in infected cells, which includes RNAP II degradation, hCLE protein levels increase throughout infection in a virus replication-dependent manner. Human and avian influenza viruses of various subtypes increase hCLE levels, but other RNA or DNA viruses do not. hCLE colocalises and interacts with viral ribonucleoproteins (vRNP) in the nucleus, as well as in the cytoplasm late in infection. Furthermore, biochemical analysis of purified virus particles and immunoelectron microscopy of infected cells show hCLE in virions, in close association with viral vRNP. These findings indicate that hCLE, a cellular protein important for viral replication, is one of the very few examples of transcription factors that are incorporated into particles of an RNA-containing virus.

Key Role of the Influenza A Virus PA Gene Segment in the Emergence of Pandemic Viruses

“…The other two proteins of note, UBA52 and CLE, appear to be involved in viral replication by as of yet undefined mechanisms [59,61]. CLE was also detected in purified IAV virions where it may be bound to viral ribonucleoprotein complexes [62]. It is unclear whether the presence of host adaptive mutations in PA modulates its interaction with any of these host factors.…”

Host Determinants of Influenza RNA Synthesis

“…hCLE was first identified in yeast two-hybrid screens as an interactor with influenza virus PA, specifically binding to its C-terminal region. hCLE localizes to vRNPs during infection and, unlike Pol II and CHD1, is progressively upregulated during infection (36,43,44). Besides colocalizing with vRNPs in the nucleus, hCLE remains associated in the cytoplasm after export and is found in released viral particles.…”

Late stages of the influenza A virus replication cycle—a tight interplay between virus and host

“…Recently, it was shown that hCLE interacts with vRNPs in the cytoplasm where it colocalizes with Rab11, PA and NP (Rodriguez-Frandsen et al, 2016). Interestingly, hCLE appears to remain attached to vRNPs during further routing of the viral genome and is even incorporated into budding viral particles (Rodriguez-Frandsen et al, 2016). However, the function of hCLE binding to vRNPs during vRNP transport and packaging remains to be determined.…”

“…hCLE, a cellular transcription factor, associates with vRNPs in the nucleus where it promotes viral polymerase and Pol II activity (Huarte et al, 2001;Rodriguez et al, 2011). Recently, it was shown that hCLE interacts with vRNPs in the cytoplasm where it colocalizes with Rab11, PA and NP (Rodriguez-Frandsen et al, 2016). Interestingly, hCLE appears to remain attached to vRNPs during further routing of the viral genome and is even incorporated into budding viral particles (Rodriguez-Frandsen et al, 2016).…”