Guest list or black list: heritable small RNAs as immunogenic memories.
Small RNA-mediated gene silencing plays a pivotal role in genome immunity by recognizing and eliminating viruses and transposons that may otherwise colonize the genome. However, individual genomic parasites are highly diverse and employ multiple immune-evasion techniques, making this silencing challenging. Here I review a new theory proposing that the integrity of the germline is maintained by transgenerationally transmitted RNA 'memories' that record ancestral gene expression patterns and delineate 'self' from 'foreign' sequences. To maintain such recollection, two tactics are employed in parallel: 'black listing' of invading nucleic acids and 'guest listing' of endogenous genes. Studies in several organisms have shown that this memorization is used by the next generation of small RNAs to act as 'inherited vaccines' that attack invading elements or as 'inherited licenses' that permit the transcription of autogenous sequences.
Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel 69978; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel 69978. Electronic address: odedrechavi@gmail.com.
Oded
O
Rechavi
D000818:Animals; D005854:Germ Cells / Q000276:immunology; D006801:Humans; D055261:Immunogenetic Phenomena; D007156:Immunologic Memory; D034622:RNA Interference / Q000276:immunology*; D034741:RNA, Small Interfering / Q000276:immunology* / Q000378:metabolism
D034741:RNA, Small Interfering
inherited immunity; inherited vaccines; self versus non-self; small RNA; transgenerational inheritance