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...