Small RNAs,RNAi and the Inheritance of Gene Silencing in Caenorhabditis elegans

Invasive nucleic acids such as transposons and viruses usually exhibit aberrant characteristics,e.g.,unpaired DNA or abnormal doublestranded RNA.Organisms employ a variety of strategies to defend themselves by distinguishing self and nonself substances and disabling these invasive nucleic acids.Furthermore,they have developed ways to remember this exposure to invaders and transmit the experience to their descendants.The mechanism underlying this inheritance has remained elusive.Recent research has shed light on the initiation and maintenance of RNA-mediated inherited gene silencing.Small regulatory RNAs play a variety of crucial roles in organisms,including gene regulation,developmental timing,antiviral defense,and genome integrity,via a process termed as RNA interference（RNAi）.Recent research has revealed that small RNAs and the RNAi machinery are engaged in establishing and promoting transgenerational gene silencing.Small RNAs direct the RNAi and chromatin modification machinery to the cognate nucleic acids to regulate gene expression and epigenetic alterations.Notably,these acquired small RNAs and epigenetic changes persist and are transmitted from parents to offspring for multiple generations.Thus,RNAi is a vital determinant of the inheritance of gene silencing and acts as a driving force of evolution.

The SNAPc complex mediates starvation-induced trans-splicing in Caenorhabditis elegans

Dietary restriction usually suppresses biosynthesis but activates catabolic pathways in animals.However,the short-term starvation enhances biosynthetic activities and promotes ribosomal biogenesis in adult Caenorhabditis elegans.The mechanism underlying the processes remains largely unknown.Here,we find that the short-term starvation enhances the SL1 trans-splicing of translation-related genes in adult C.elegans by transcriptome analysis.The small nuclear RNA-activating protein complex(SNAPc)promotes SL RNA production and mediates starvation-induced trans-splicing.TOFU-5,a core factor in the upstream sequence transcription complex(USTC)essential for piRNA production,is also involved in the starvationinduced trans-splicing processes.Knocking down components of the SNAPc complex and tofu-5 extends worm survival under starvation conditions.Taken together,our study highlights the importance of SL transsplicing in the nutrition response and reveals a mechanism of the survival regulation by food deprivation via SNAPc and TOFU-5.