Table 1.

Mechanisms for miRNA sorting

References	Regulating factor	Mechanisms	miRNA examples
Villarroya-Beltri et al. 2013 [20]	GGAG motif	Nuclear ribonucleoprotein A2B1 binds GGAG in miRNAs.	miR-198 and miR-601
Santangelo et al. 2016 [21]	GGCU motif	Synaptotagmin-binding cytoplasmic RNA-interacting protein (SYNCRIP) recognizes GGCU motif in miRNAs.	miR-3470a and miR-194-2-3p
Koppers-Lalic et al. 2014 [22]	3′-End uridylation	3′-End posttranscriptional modification with uridylation demarcates EV miRNAs.	miR-486-5p
Gibbings et al. 2009 [23] and McKenzie et al. 2016 [24]	Ago 2	1. Ago2 binds with miRNAs to form the RISC. 2. RISC associates with MVB to control miRNA sorting.	let-7a, miR-100, and miR-320a
Iavello et al. 2016 [25]	Alix	Alix binds to Ago2 and miRNAs.	miR-24, miR-31, and miR-125b
Lu et al. 2017 [26]	MEX3C	MEX3C binds with AP-2 and promotes miR-451a sorting.	miR-451a

miRNAs microRNAs, EV extracellular vesicle, Ago2 argonaute 2, RISC RNA-induced silencing complex, MVB multivesicular bodies, AP-2 adaptor-related protein complex 2