Step-by-step explanation:
RNA polymerase II is the enzyme that is responsible for the transcription of the DNA into the mRNA molecule in the eukaryotes.
The polymerase activity of RNA polymerase II is due to a specific sequence of nucleotides present at the C terminal end of protein and it is this C terminal domain that the RNA polymerase enzyme is involved in transcription, splicing, and capping.
If a toxin, in case binds to the C terminal of this domain then all of these functions will be disturbed and the enzyme will not be able to perform its function and the cell would be dead.