A total of 10 single nucleotide mutations have been introduced into all six RNP motifs of the three RRMs of the elav coding sequence. This results in the following amino acid substitutions: Y205A and F207D (in RRM1, RNP1), I152A and N154A (in RRM1, RNP2), F294A (in RRM2, RNP1), Y251A (in RRM2, RNP2), Y445A and F447D (in RRM3, RNP1), F405A and Y407A (in RRM3, RNP2). In addition, sequence encoding the Tag:FLAG and Tag:HA epitopes has been inserted into the endogenous fne locus, at the N-terminal end of the open reading frame.