eIF4A1/2 function in mitotic exit and chromatin decondensation

• Applicant: Professor Dr. Wolfram Antonin
• Subject Area: Cell Biology
• Term: since 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 107479298

During mitosis, the nucleus undergoes significant structural and functional reorganization. In animal cells, the nuclear envelope disintegrates at the onset of mitosis, leading to the extensive condensation of chromatin into distinct chromosomes. These chromosomes are captured and segregated by the spindle apparatus, a series of processes that have been extensively studied. However, much less is understood about how the interphase state of the nucleus is reestablished at the conclusion of mitosis, enabling it to perform its diverse functions. This restoration involves the decompaction of highly condensed mitotic chromosomes, a crucial step for reinitiating transcription and perpetuating genomic information, thus playing a central role in the cellular life cycle. Despite its importance for fundamental research and potential medical implications, mitotic chromatin decondensation remains poorly defined. While cytological descriptions have been established early on, there is still limited understanding of the underlying molecular events and mechanisms involved. In the previous funding period, we identified the DEAD-box helicases eIF4A1/2 as essential factors for chromatin decondensation at the end of mitosis. In this context, eIF4A1/2 functions as an RNA chaperone that regulates the composition and likely fluidity of the perichromatin layer, an RNA-protein condensate located on the surface of mitotic chromosomes. Notably, this activity of eIF4A1/2 operates independently from its well-characterized roles in translation initiation but is vital for the dynamic reorganization of chromatin as cells transition out of mitosis. Building on these findings, we will now determine precisely when and where eIF4A1/2 acts during mitosis while exploring its functional implications on perichromatin RNA condensates and their contributions to chromatin dynamics. For this, we will use an inducible eIF4A1-degron cell line that enables rapid degradation of eIF4A1 in combination with live cell imaging. We will identify specific RNAs targeted by eIF4A1/2 throughout mitosis through RNA immunoprecipitations and investigate their roles in facilitating chromatin decondensation. Additionally, we will examine synergistic interactions between Ki-67, a key organizer of the perichromatin layer, and eIF4A1/2 in regulating chromatin structure during cell division and mitotic exit using a combination of biochemical reconstitution, cell-free, and cellular assays. Our research aims to illuminate this poorly understood yet critical cellular process occurring at the end of mitosis that is indispensable for restoring nuclear structure and function.

• DFG Programme: Research Grants