A tripartite mechanism licenses RNA polymerase import into the phage nucleus
Nucleus-forming jumbo phages import a phage-encoded non-virion RNA polymerase (nvRNAP) into a proteinaceous nucleus, but how it is selected for import is unknown. Here, we identify an import pathway that couples nvRNAP subunit interactions with phage-encoded import factors. Maximal nvRNAP import requires a novel factor Imp7 (gp166) and the essential import factor Imp1. Imp7 is essential at…
Phage-encoded RNA polymerase, a non-virion subunit, is imported into the nucleus of jumbo phages. However, the mechanism governing this import remains unclear. Researchers have now identified a pathway that links the subunit interactions of the non-virion RNA polymerase (nvRNAP) with specific import factors. This pathway necessitates two key factors, Imp7 (gp166) and Imp1, for efficient nvRNAP import.
Essential at room temperature (20°C), the absence of Imp7 results in diminished middle and late transcription, ultimately hindering phage DNA replication. Importantly, each individual nvRNAP subunit's import relies on other subunits, suggesting that import licensing occurs at the level of an assembled complex. Despite the absence of middle transcription and DNA replication, the phage nucleus continues to assemble and segregate from the cytoplasm.
This finding indicates that nvRNAP nuclear localization and activity are not crucial checkpoints for nucleus assembly. Overall, these results unveil a specialized import pathway for the multi-subunit RNA polymerase and reveal that the nuclear compartment assembly occurs prior to the transcriptional and replicative programs necessary for its maturation.
Written by urgent.news from bioRxiv's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
