We have no official publication requirement. The amount of work considered worthy of a thesis is determined by the thesis committee. Most students end up graduating with at least a few publications because the amount of work they do ends up being sufficient for at least that number.
While I realize this may be unconventional, I look at the publications as incidental to (or perhaps supportive of) your actual work done during the thesis. Getting work published in a scientific journal is not a simple matter of quality or amount of work done. There are politics involved, a judgement by the editor whether your paper is a "sexy" topic, the issue of having a "complete story" with mechanistic insight versus "descriptive" work, and many others. Faculty on committees (should) realize the reality of this. So if you have done solid work that they feel merits the PhD, then that is all you need. In fact, there have been a couple of cases in our program in which a student graduated without any publications. Of course, it is probably much easier to convince your thesis committee that it is time to move on if you can tell them you have already published your work in a number of papers.