in most cases (in MTTs especially) you shouldn"t 3bet AQ to a button raiser if you are going to fold to a 4bet - you might as well 3bet with 72o as it is basically a bluff. Have a plan before you 3bet, don"t just go ZOMG i have AQ let"s 3bet without thinking about what comes next, which is why stack sizes are so important.
loads of factors come into play - stacks, position, blinds, table image of all involved etc etc etc
agreed AQ doesn"t stand up well vs most people"s 4betting range but think about that before 3betting in the first place.
in later stages of MTTs, 3bet/folding is just spew, with 100bb etc then it can be fine depending upon circumstances.
edit - just seen the 100bb+ part - not happening very often in MTTs and will occur in cash, therefore it is very player read dependant - also consider whether it is 6max or full ring etc