I found two references citing papers in Nature for CBO:
Kwok, R.P.S.; Lundblad, J.R.; Chrivia, J.C.; Richards, J.P.; Bachlinger, H.P.; Brennan, R.G.; Roberts, S.G.E.; Green, M.R.; Goodman, R.H. Nuclear protein CBO is a coactivator for the transcription factor CREB. Nature 1994, 370, 223-226. (reference 44 here
Chakravarti D, LaMorte VJ, Nelson MC, Nakajima T, Schulman IG, Juguilon H, Montminy M and Evans R (1996) Role of CBO/p300 in nuclear receptor signalling. Nature, 383, 99–103. (in references here
However, when you look these references up at Nature, the CBO in the title of the cited publications is changed to CBP...