Snape and the Defense Against the Dark Arts Job

[sawsan_issa]

No: HPFGUIDX 87327

I read that JKR had said that Snape can't get the Defense Against the
Dark Arts job  because Dumbledore feels that it will cause Snape's bad
side (as if it could get worse) to come out. That intrigues me. What
do you think the reason is? What is it about the Defense Against the
Dark Arts job that will bring out the evil in Snape?