Chartboost—a gaming tech company. (We were way off—we predicted Argentina would win the space.) Currently in SoMa, it's zipping up to 420 Taylor, aka Practice Fusion's former home.

Chartboost is expanding big time from 303 2nd by moving into the 46k SF Union Square building. The new lease kicks in in July, Seal Rock Investments founder Brian Veit tells us. Chartboost will be subleasing the space, as is, for $50/SF, he says. In a month, the Practice Fusion signage will be replaced with Chartboost (apologies for our rudimentary Perez Hilton graphic, but you get the gist).

Practice Fusion's lease is up in October 2016 at 420. Here's a photo of the building when built; it was the first air-conditioned building in S.F. in 1941 when it was NBC's radio studios. Meanwhile, the medical records company's new 100k SF space at Zynga's HQ is double the size of its former home, spread out over two floors. Though the floor plates are more massive, we hear ceilings are lower than those at 420.