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Fig. 3 | Acta Neuropathologica Communications

Fig. 3

From: RNA biology of disease-associated microsatellite repeat expansions

Fig. 3

Possible mechanisms of nuclear and cytoplasmic RNA surveillance, nuclear export, and translation of xtrRNA. RNA containing large repeat expansion sequences may be subject to nuclear RNA surveillance mechanisms, including degradation by the nuclear exosome (1) or the XRN2 5'-3' exoribonuclease (1). Export of xtrRNA likely involves bulk mRNA transport via NXF1 (2b), but may also include alternative mechanisms like CRM1-mediated export (2a) or possibly nuclear envelope budding (2c). Cytoplasmic RNA surveillance mechanisms that may control xtrRNA levels and translation include nonsense-mediated decay (NMD) (3a), no-go decay (NGD) (3b), or nonstop decay (NSD) (3c). Translation of xtrRNA is likely to follow canonical cap-dependent translation (4), especially when repeat expansions are embedded in normal coding regions of an mRNA, but may potentially involve internal ribosome entry site (IRES)-like mechanisms (4). RAN translation has been shown to be cap-dependent for some repeat expansions, but complete mechanistic details remain to be determined

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