UNC-104 is an ATP-dependent kinesin motor necessary for the transport of synaptic vesicle proteins from the cell body to the synapse. UNC-104 has been shown to be degraded at synapses through ubiquitin-mediated pathways depending on its ability to bind cargo. Ubiquitination is also known to regulate protein function without leading to degradation. Thus we investigated whether, in addition to degradation, ubiquitination of UNC-104 can alter motor function. To identify E3s that ubiquitinate UNC-104, we carried out a Touch Receptor Neuron-specific RNAi screen of 230 neuronally enriched E3 ubiquitin ligases. We identified F54B11.5 (an RNF141 orthologue) as a potential regulator of ubiquitination of UNC-104. We observe UNC-104 has an anterograde bias in the following three assays:- motor accumulation at the site of laser ablation, UNC-104 particle tracking, and Fluorescence Recovery after Photobleaching (FRAP). In RNAi of the E1 ubiquitin-activating enzyme,
uba-1, and
f54b11.5, UNC-104's anterograde bias is increased in an ATP-dependent manner. Likewise, using FRAP, we observe a reduction in UNC-104's retrograde diffusive flux in an
uba-1 mutant. These observed alterations of biased UNC-104 movement result in
uba-1 and
f54b11.5 RNAi may lead to the observed increase in anterograde net displacement of the synaptic vesicle protein RAB-3. These data suggest a hypothesis where the lack of UNC-104 degradation leads to a greater that number of motors on the cargo surface as opposed to the freely diffusing UNC-104. Together, these data suggest that ubiquitination may regulate UNC-104's ability to bind cargo and maintain an equilibrium of UNC-104's anterograde and retrograde flux.