To effectively run a game at 4 with 60 fps, your graphic card needs at least 6GBs of VRAM on it. I know for a fact that the 980 does not as I have the same card and it only has 4GBs.

NOTE: I am not saying that this the only thing you need to look at, I just know this is the minimum requirement or else you cannot get consistently 60 fps at 4k.

EDIT: In response to the post that was made while I was typing mine out, the 1070 has 8GBs of VRAM.