F. Bovia et al., THE SRP9 14 SUBUNIT OF THE HUMAN SIGNAL RECOGNITION PARTICLE BINDS TOA VARIETY OF ALU-LIKE RNAS AND WITH HIGHER AFFINITY THAN ITS MOUSE HOMOLOG/, Nucleic acids research, 25(2), 1997, pp. 318-325
The heterodimeric subunit, SRP9/14, of the signal recognition particle
(SRP) has previously been found to bind to scAlu and scB1 RNAs in vit
ro and to exist in large excess over SRP in anthropoid cells, Here we
show that human and mouse SRP9/14 bind with high affinities to other A
lu-like RNAs of different evolutionary ages including the neuron-speci
fic BC200 RNA, The relative dissociation constants of the different RN
A-protein complexes are inversely proportional to the evolutionary dis
tance between the Alu RNA species and 7SL RNA. In addition, the human
SRP9/14 binds with higher affinity than mouse SRP9/14 to all RNAs anal
yzed and this difference is not explained by the additional C-terminal
domain present in the anthropoid SRP14. The conservation of high affi
nity interactions between SRP9/14 and Alu-like RNAs strongly indicates
that these Alu-like RNPs exist in vivo and that they have cellular fu
nctions, The observation that human SRP9/14 binds better than its mous
e counterpart to distantly related Alu RNAs, such as recently transpos
ed elements, suggests that the anthropoid-specific excess of SRP9/14 m
ay have a role in controlling Alu amplification rather than in compens
ating a defect in SRP assembly and functions.