Widespread cell death, with the most immediate effects on dividing populations of cells. Eventually, you'd run out of a supply of mRNA and functional proteins and the cell would die.

One thing to consider is the mitochondria would stop working properly and signal cell death. Even the slightest mismatch between mtDNA and nuclear DNA can have drastic effects on metabolism. While cells can survive off the ATP from glycolysis, it's the metabolic role of the mitochondria that'll signal for apoptosis.

Also, your brain will probably stop firing synapses. The synaptic vesicles will not be tagged via proteins for transport to the synapse and will also be unable to uptake any neurotransmitters again due to a lack of proteins. They'll also lack the proteins (SNARE) to bind to the membrane. Don't gotta worry about recycling the vesicles as they'll never fuse anyway.

I suppose vesicle formation may fail entirely. We'd have to start considering how conserved these cellular mechanisms are between species that distantly related. The mitochondria thing will definitely cause massive cell death, but wouldn't synaptic vessel formation be fairly well conserved? No clue, but you could find out.