...is necessary for Alu mobilization, although the binding of two heterodimers provides more efficient mobilization. Alu RNPs, once formed, can dock on ribosomes. As L1 mRNA is translated, the poly(A) tail of an SRP9/14-bound Alu competes for nascent L1 ORF2 reverse transcriptase ( Sinnett et al. 1991 ; Boeke...