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. 2020 Jun 11;147(11):dev175786. doi: 10.1242/dev.175786

Fig. 1.

Fig. 1. Retrotransposons may influence multiple pillars of aging. (A) L1 and Alu retro-elements are the most abundant transposable elements (TEs) in the human genome. A stereotypical L1 (top) and Alu (bottom) are displayed. (Top) Human L1s are typically ∼6 kb long TEs with flanking target site duplications (TSDs). There is a bidirectional promoter in the 5′ UTR, as well as two open reading frames (ORFs): ORF1 and ORF2. ORF1 encodes a RNA-binding protein with nucleic acid chaperone activity; ORF2 encodes an endonuclease (EN) and reverse transcriptase (RT). An additional ORF in the antisense orientation, ORF0, is present in the 5′ UTR of primate L1. For simplicity, ORF0 is not depicted here. (Bottom) Alu elements are typically 100-300 bp, with flanking target site duplications (TSDs). They usually contain a left Alu monomer with A- and B-box promoters, and a right Alu monomer. Alu elements are non-autonomous and use the L1 machinery for transposition. (B) TE activity can lead to genomic instability through insertional mutagenesis or double-stranded DNA breaks. (C) TE upregulation in senescent cells (and in the absence of Sirt6) correlates with an inflammatory secretory phenotype, notably with the production of type I interferons. (D) Emerging evidence suggests that TEs can interact with mitochondria, which may lead to mitochondrial dysfunctions.

Retrotransposons may influence multiple pillars of aging. (A) L1 and Alu retro-elements are the most abundant transposable elements (TEs) in the human genome. A stereotypical L1 (top) and Alu (bottom) are displayed. (Top) Human L1s are typically ∼6 kb long TEs with flanking target site duplications (TSDs). There is a bidirectional promoter in the 5′ UTR, as well as two open reading frames (ORFs): ORF1 and ORF2. ORF1 encodes a RNA-binding protein with nucleic acid chaperone activity; ORF2 encodes an endonuclease (EN) and reverse transcriptase (RT). An additional ORF in the antisense orientation, ORF0, is present in the 5′ UTR of primate L1. For simplicity, ORF0 is not depicted here. (Bottom) Alu elements are typically 100-300 bp, with flanking target site duplications (TSDs). They usually contain a left Alu monomer with A- and B-box promoters, and a right Alu monomer. Alu elements are non-autonomous and use the L1 machinery for transposition. (B) TE activity can lead to genomic instability through insertional mutagenesis or double-stranded DNA breaks. (C) TE upregulation in senescent cells (and in the absence of Sirt6) correlates with an inflammatory secretory phenotype, notably with the production of type I interferons. (D) Emerging evidence suggests that TEs can interact with mitochondria, which may lead to mitochondrial dysfunctions.