The role of hnRNPC in translation during mitosis

Mitosis is a dynamic process controlled by various mechanisms which ensures correct cell division. During mitosis global translation is decreased to 35%, but the translation of some mRNAs escapes this suppression. Proteomic analysis of polysomes in mitotic cells showed an enrichment of the polysomes with nuclear proteins, especially hnRNPC. Puromycin-sensitivity assay and polysome profiling revealed the association of hnRNPC with elongating ribosomal complexes during mitosis. RT-qPCR experiment revealed that mRNAs encoding selected ribosomal proteins are associated with heavy polysomes in mitosis, only in the presence of hnRNPC. Immunofluorescence experiments presented a unique mitotic phenotype of hnRNPC, localized to the cell periphery during metaphase together with RPS6.

To further investigate the role of hnRNPC in translation during mitosis, an improved synchronization procedure was applied. Cells were synchronized to metaphase using proTAME, or to G2 using a CDK1 inhibitor (RO-3306). This allows clear and more precise separation between G­2 and M phases of the cell cycle. Polysome profiling exposed that hnRNPC is heavily associated with polysomes during metaphase but not in G2. To identify additional proteins that assist the role of hnRNPC in translation regulation during mitosis, co-immunoprecipitation experiments are currently performed.