Fig. 4: A class of snoRNA-intron napRNAs (snotrons). | Nature Communications

Fig. 4: A class of snoRNA-intron napRNAs (snotrons).

From: NAP-seq reveals multiple classes of structured noncoding RNAs with regulatory functions

Fig. 4

Statistics of the distances from napRNAs to annotated snoRNAs: start sites (a) and end sites (b). The x-axis shows the distance (nt) from napRNA 5’-start (or 3’-end) sites to snoRNA 5’-start (or 3’-end) sites, and the y-axis shows the number of napRNAs within the specified distance range. Genome Browser view of 5’-start, 3’-end and coverage signals (RPM, reads per million) in an extended region of two snotrons: hsa-snotron-1 (c) and mmu-snotron-5 (d). The highly stable secondary structures of snotron hsa-snotron-1 (e) and mmu-snotron-5 (f). g Verification of hsa-snotron-1 by irNorthern blotting in HepG2 cells. Source data are provided as a Source Data file. h Cumulative curves and box plots showing the distance from the host 3’-SS to the snoRNA 3’-end sites (n = 35 examined over 17 independent experiments) identified by NAP-seq and to the other snoRNA 3’-end sites (n = 363 according to the snoRNAbase). p value was calculated by two-sided Mann–Whitney–Wilcoxon test. Each boxplot shows the minima, maxima, center, bounds of box, whiskers, first and third percentile. i The proposed model of snotron biogenesis. An intron lariat is spliced from the host gene and is then debranched to generate a linear intron. Next, the RNA splicing intermediate is processed into a C/D box snoRNA or an H/ACA box snoRNA after the lariat intron is debranched (left path). Because the 3’-ends of shorter linear introns are formed into complex structures quickly and bind to RBPs, making the exonuclease unable to cut them, these intronic RNAs are stable as snotrons (right path). In addition, cellular stress might suppress snotron formation.

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