RNA-binding protein which forms ribonucleoprotein complexes (RNPs) that play critical roles in the localization, translational repression and turnover of RNAs during embryogenesis, neurotransmission and neurogenesis (PubMed:10698941, PubMed:1712672, PubMed:8001156, PubMed:17178403). In the oocyte, essential for the localization of both the osk/oskar mRNA to the posterior pole and bcd/bicoid RNA to the anterior pole, and is therefore required for the correct anterior-posterior patterning of the developing embryo (PubMed:10698941, PubMed:1712672, PubMed:8001156). Association with osk or bcd at their respective poles, appears to promote the formation and stabilization of the ribonucleoprotein complexes (PubMed:1712672, PubMed:8001156). Integral component of diverse neuritic ribonucleoprotein complexes (RNPs) that mediate the transport, translation and turnover of neuronal RNAs during neuorgenesis and the translation repression of synaptic transcripts in preparation for their dendritic targeting (PubMed:17178403). Component of neuronal ribonucleoprotein complexes (RNPs) that contains at least various translational repressor and mRNA turnover proteins such as me31B, tral, Upf1, AGO2 and sometimes Fmr1. Detected within ribonucleoprotein granules in pherpiheral nerves that are exiting the larval central nervous system, and cell bodies within the ventral ganglion. Polar granules at the posterior pole of the oocyte, and by the time the egg is laid, at the anterior pole. Expressed both maternally and zygotically. Contains a proline-rich domain. The insertion of this domain in the DRBM 2 domain is required for stau-oskar mRNA localization. DRBM 3 domain binds optimally to stem-loops containing 12 bp (in vitro).