RNA memory

In the last decade non-coding RNAs (ncRNAs) have emerged as cellular key regulators. The attention of the scientific community has focused on ncRNAs with repressive features on eukaryotic transcriptional regulation. Many experimental evidences suggest that ncRNAs could also positively regulate transcription. The RNA-Memory Model (Arancio W. Rejuvenation Res. 2010 Apr-Jun;13(2-3):365-72.) gives possible explanations to several biological phenomena via trans-acting ncRNAs (memRNAs) able to orchestrate chromatin remodelling and in turn enhance transcription. memRNAs assert their functions especially during the post-mitotic chromatin remodelling. memRNAs can mark the genes transcribed in the mother cell that must be re-activate after the cell division. During the M phase of the cell cycle the chromatin is almost totally collapsed and the transcription is turned off. RNA memory model explains easily how the epigenetic state can be re-established after mitosis. RNA memory, e. g., can easily explain why the interference machinery is needed for the establishment of the silenced state of a gene but it is not needed for its maintenance: the interference machinery drives the degradation of specific memRNAs in the mother cell; so in the next cell generation the gene is maintained silenced, and so on through generations, if no external stimuli perturb the state. RNA memory model fits perfectly with other models on the epigenetic inheritance (epigenetic histone code readers/writers, histone variants, PcG/trxG interaction, structural epigenetic memory, etc). The relationship of RNA memory with other models will be discussed specifically. An RNA-Memory model explanation of controversial biological phenomena will be suggested. If the model is correct, the impact in the comprehension of transcriptional regulation events could be enormous