What Is The Role Of Rna Polymerase – Transcription in eukaryotic cells is carried out by three RNA polymerases. RNA polymerase I synthesizes most rRNAs, while RNA polymerase II transcribes all mRNAs and many non-coding RNAs. The largest of the three polymerases is RNA polymerase III (Pol III) which transcribes a number of short non-coding RNAs including tRNAs and the 5S rRNA, as well as other small RNAs such as snRNAs, snoRNAs, SINEs, 7SL RNA, Y RNA , and splceosomal U6 RNA. Pol III-mediated transcription is dynamic and regulated in response to changes in cell growth, cell proliferation and stress. Transcripts generated by Pol III are involved in a wide variety of cellular processes, including translation, genome and transcriptome regulation and RNA processing, with Pol III dys-regulation implicated in diseases that ‘ including leukodystrophy, Alzheimer’s, Fragile X-syndrome and various cancers. Recently, Pol III was identified as an evolutionarily conserved effector of organismal life acting downstream of mTORC1. Inhibition of Pol III extends lifespan in yeast, worms and flies, and in worms and flies work from individual intestinal and intestinal cells to achieve this. Interestingly, Pol III activation achieved through the attenuation of its main repressor, Maf1, has been shown to promote longevity in model organisms, including mice. In this review we introduce the transcriptional machinery of Pol III and review the current understanding of the role of RNA Pol III in aging and longevity in the various model organisms. We then discuss the potential of Pol III as a therapeutic target to improve age-related health in humans.

Transcription of the eukaryotic nuclear genome is carried out by three conserved multi-subunit RNA polymerases (Pols), each of which transcribes a specific set of genes. A large portion of the nuclear genome is transcribed by Pol II to generate coding and non-coding RNAs. In contrast, Pol I transcribes only one gene, although it is present in multiple copies within the genome, to produce the precursor to most rRNAs. result While Pol I and III transcribe fewer genes, they generate some of the most abundant cellular RNAs accounting for much of the cellular transcriptional activity (White, 2008; Vannini and Cramer, 2012; Arimbasseri and Maraia, 2016).

What Is The Role Of Rna Polymerase

With 17 subunits, Pol III is the largest of the three RNA polymerases (Vannini and Cramer, 2012). It transcribes several abundant, non-coding RNAs (up to a few hundred bases in length), some of which are involved in translation, such as the 5S rRNA and tRNAs, some of which are involved in RNA processing , such as several sn or snoRNAs, but others, such as 7SK RNA, have regulatory roles. Indeed, the list of Pol III transcribed genes has been expanding recently (Acker et al., 2013; Turowski and Tollervey, 2016). The function of Pol III has also expanded beyond its canonical role in the transcription of the nuclear genome to now include responses to DNA viruses and homologous-mediated repair of DNA double-strand breaks (Chiu et al., 2009; Liu et al., 2021). Pol III mediated transcription is involved in a wide range of biological processes including cell and organism growth (Grewal et al., 2005, 2007; Halaschek-Wiener et al., 2005; Chiu et al., 2009; Marshall et al., 2012; Rideout et al., 2012), cell cycle (White et al., 1995), stability and differentiation (Wong et al., 2011; Alla and Cairns, 2014 ; Van Bortle et al., 2017; Chen et al., 2018), development (Schmitt et al., 2014), regeneration (Yeganeh et al., 2019), and cellular responses to stress (Upadhya et al., 2002; Gouge et al., 2015). As a result, Pol III subunits have been implicated in a wide range of disease states, reviewed by (Yeganeh and Hernandez, 2020).

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The recruitment of Pol III to its target genes is facilitated by several specific, basal transcription factors (TFs), where the exact combination of TFs involved is determined by the specific promoter present (on reviewed in Schramm and Hernandez (2002).promoter (Type I-III) recruits Pol III, all three requiring binding of TFIIIB, TF 3-subunit containing TATA box binding protein (TBP) . resides in the 5′ flanking region. Type II is present in tRNA genes and additionally requires TFIIIC, a 6-subunit TF that binds intragenic promoter elements. direct binding of TFIIIC Type III is between -different from Type I and II promoters in that they do not require TFIIIC for Pol III-mediated transcription but recruit SNAPc, a TF also associated with Pol II transcription (Schramm and Hernandez, 2002). types and TFs are largely conserved ​​over wide evolutionary distances but with some phyla-specific differences (Schramm and Hernandez, 2002; Teichmann et al., 2010). Additional TFs that regulate Pol III activity include Myc, a transcriptional activator that acts on all three Pols (Gomez-Roman et al., 2003; Campbell and White, 2014), which as well as the Maf1 protein, a highly conserved Pol III. activity (Upadhya et al., 2002; Vorländer et al., 2020). Given the critical functions of RNA Pol III in growth and differentiation, it is perhaps not entirely surprising that the signaling pathways that influence these cellular processes can interact and regulate Pol III activity (Willis and Moir , 2018). Perhaps the most studied of these is the highly conserved mTOR pathway (Wei et al., 2009; Liu and Sabatini, 2020), which we will ‘ discussed in the next section.

The increasing number of elderly people in our societies has stimulated the study of aging biology in the hope that a detailed understanding of aging mechanisms will lead to the identification of targets for intervention to help preventing or reducing aging diseases (Partridge et al. , 2018). In fact, several decades of research have shown that aging itself is very plastic and can be modulated through genetic, dietary and pharmaceutical methods. For example, reduction in the activity of Target of Rapamycin kinase Complex 1 (TORC1) can promote longevity and health in several animal species (Erdogan et al., 2016; Liu and Sabatini, 2020). The main component of the mTOR complex is a 289 kDa Ser/Thr kinase that belongs to the PI3K-related protein kinase (PIKK) family (Liu and Sabatini, 2020). TORC1 is activated in the presence of nutrients and growth factors, essentially acting to promote anabolic pathways while suppressing catabolism. Since protein synthesis is one of the most energy-intensive anabolic processes necessary for growth (Buttgereit and Brand, 1995), TORC1 tightly regulates the supply of protein synthetic machinery, including the regulation of Pol III activity. . Indeed, TORC1 has also been shown to localize to the promoters of several rRNA and tRNA genes and control their transcription (Li et al., 2006). It is this link between TORC1 and Pol III that first led us to investigate the role of Pol III in biological aging.

It is possible to reduce the activity of RNA Polymerase III in model organisms by reducing individual subunits of this complex, through a partial or limited loss of activity, thus avoiding the death of the organism that follows the loss total We found that in the nematode Caenorhabditis elegans, RNAi targeted the rpc-1 gene, which encodes the largest of the 17 Pol III subunits (orthologue of yeast RPC160) , significantly extended the lifespan of an organism (Filer et al., 2017). This was also the case in the fruit fly Drosophila melanogaster, where RNAi of dC160 (the fly orthologue of RPC160) extended lifespan, as did a heterozygous mutant of another Pol III subunit dC53 (Filer et al., 2017 ). In fact, irreversible loss of RPC160 in yeast extended life spans historically, thus demonstrating extensive evolutionary conservation (Filer et al., 2017).

Since the longevity of an organism can be determined by a specific organ, we tested whether this was also true for Pol III (Filer et al., 2017). Because the intestine has previously been shown to be important for modulating longevity in both worms and flies, we focused on this tissue (Libina et al., 2003; Piper et al., 2008). We showed that inhibition of Pol III activity in the adult worm or fly gut using tissue-specific RNAi was sufficient to extend lifespan; and specifically in flies, longevity was also achieved by Pol III inhibition only within intestinal stem cells (ISCs) (Filer et al., 2017). In contrast, Pol III depletion in neurons and the fat body of flies had little or no effect on lifespan (Filer et al., 2017).

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With advancing age, the function of many organ systems and tissues declines, contributing to physiological decline, multiple diseases and ultimately death (Rera et al., 2012; Ezcurra et al., 2018; Funk et al., 2020). For example, in worms and flies the intestinal luminal wall begins to break down and become more rigid with advancing age, with similar changes in intestinal permeability and barrier function reported in mammals. , including humans (Funk et al., 2020). We found that the longevity caused by Pol III knockdown was associated with the development of age-related gut pathology and the subsequent functional decline (Filer et al., 2017). This crucially indicates that Pol III reduction is both a target for longevity and for age-related health, and together with the longevity data the gut longevity points are intense.

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