Exploring mRNP packaging throughout the nucleus

During transcription and mRNA processing, many proteins associate with the transcript to form a protein-RNA particle, termed the mRNP. Little information is available regarding the restructuring of the mRNP during its nuclear travels and the organization of the transcript within the particle. While it is known that remodeling of protein components of the mRNP takes place during different steps of the way, it is unclear whether the mRNP undergoes organizational changes while moving through the nucleoplasm, and if so, how and where do they occur.

To understand mRNP organization and remodeling in the nucleus, we have been using STED super-resolution microscopy to examine the degrees of compaction of the mRNP particle via the internal organization of the mRNA within, during its travels in the nucleus. In addition, we are examining whether several RNA binding factors are required for the regulation of transcript compaction within the mRNP structure.

Using a cell system, featuring a long transcript that is easily detected in the nucleus, we were able to microscopically distinguish between the 5’ and 3’ ends of the mRNA transcript. Our analysis demonstrates that the mRNA does indeed undergo conformational changes during its nucleoplasmic travels, suggesting that the nascent mRNA, adjacent to the site of transcription, and the peripheral mRNA populations are less compact than the mRNA traveling in the nucleoplasm. In addition, we demonstrate the effects of RNA-binding proteins on mRNA compaction. Altogether, this approach will allow us to characterize how the mRNA is packaged during its travels in the nucleus.