Julia was fed up with her husband. He was cruel and abusive and obviously preferred his own son by a previous marriage to her own son by a previous marriage. They were fighting constantly and he was heard complaining about his wife to his friends and threatening to divorce her.
She couldn't let that happen. It would mean a huge change in lifestyle. Julia decided to poison her husband by serving him mushrooms for dinner. She choose the "delicacy" Amanita phalloides because it was known to act quickly. By dawn the following day, her husband was dead.
Julia's husband was Tiberius Claudius Caesar Augustus Germanicus, Emperor of Rome, and the date was October 13, 54. Julia, better known as Julia Agrippina or Agrippina the Younger, moved quickly to install her son, Nero Claudius Caesar Augustus Germanicus on the throne.
Some mushrooms of the genus Amanita contain a deady poison called α-amanitin [Monday's Molecule #18: thanks to Matt for being the first to name the molecule]. α-amanitin is a potent inhibitor of eukaryotic RNA polymerase thus blocking transcription and preventing the expression of essential genes.
The story may not be true. Nobody knows for certain that Claudius was poisoned but by all acounts it seems likely. Nobody knows for certain that Agrippina prepared the meal herself but it seems very likely she was behind the assassination.
The story has entered the list of tales told in biochemistry class because it illustrates the importance of α-amanitin. It's rarely repeated in textbooks because of the historical uncertainties, but there's a famous telling of the tale in an earlier edition of Modern Biology by Postlethwait and Hopson. On page 229 they have a Box titled Caesar Experiments with RNA Synthesis,
For the first ten hours after Casear ate this delicacy, all seemed well. But as he digested the fungus, the α-amanitin entered his bloodstream and was absorbed by his liver and kidneys, where it began to block transcription. About 15 hours after his repast, with no new mRNA to make new proteins Caesar's liver cells stopped functioning, and nausea, diarrhea, and delirium began to hit him. Two days later, he died of liver failure. It is highly doubtful that Caesar learned to appreciate the valuable role of RNA polymerase in DNA transcription. But perhaps, in a general way, Agrippina did.