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. 2019 Jan 15;10(1):1–20. doi: 10.1080/21541264.2018.1558677

Figure 1.

Figure 1.

RNA processing in skeletal muscle. (a). Cross-section of a representative skeletal muscle. Individual multinucleated muscle fibers (blue dots) are bundled into fascicles. Each muscle fiber is made of myofibrils that contain the myofilaments, actin and myosin. T-tubules penetrate the muscle fiber and come into close proximity to the sarcoplasmic reticulum which surround the myofilaments. (b). Interactive view of RNA processing. After RNA polymerase-II (RNA Pol-II) transcribes DNA, newly synthesized mRNA is capped, cut and polyadenylated by the cleavage and polyadenylation factor, and then spliced. (c). Alternative splicing of a cassette exon that can either be included or skipped in the final mRNA transcript. (d). Alternative polyadenylation site selection. The 3ʹUTRs of some genes contain multiple polyadenylation signals that can be recognized by the polyadenylation and cleavage factor (CPSF). After the cleavage and polyadenylation factor binds to a polyadenylation signal (PAS), the polyA polymerase (PAP) adds the string of adenosines to the end of the mRNA transcript. This panel shows an example where three mRNA transcripts are generated by different polyadenylation site selection.