Story Identification: Series of time travel novels with historical fictional elements

Question

I recall reading these at least fifteen years ago, but they were probably written before that. It's a series of novels centered around some kind of future institute that sends people back in time. There, they recruit natives of that time period, probably genetically modifying them in the process. The way that they are funded is by locating and preserving lost works of art, which they save and sell some time in the future. Eventually, it is revealed (of course) that the institute is not all that it seems, in some vaguely sinister way. I think many of the time travelers may have been immortal.

It may have been YA, but some of the mature themes suggest otherwise.

Answer 1

That sounds like Kage Baker's The Company series -- it fits your description in detail, though I believe that the modifications made to the Dr. Zeus Company's agents are more along the lines of cyborgization than genetic modification. Whatever, it renders them nearly immortal.(See discussion in Wikipedia. There's also a website kagebaker.com about her work.)