I bought a Asus PB287Q 4k Monitor in September and I only realised that it is locked at 30 Hz for me, and I am not able to change it in any settings what so ever! I am not able to return it, but if it is a graphics card problem, I might just buy a 980, or R9 290x.
NOTE: IT IS USING DISPLAY PORT!
BTW the computer has a R9 280 and a i5 4460.