Biochemistry. In the article “The TRAP220 component of a thyroid hormone receptor-associated protein (TRAP) coactivator complex interacts directly with nuclear receptors in a ligand-dependent fashion” by Chao-Xing Yuan, Mitsuhiro Ito, Joseph D. Fondell, Zheng-Yuan Fu, and Robert G. Roeder, which appeared in number 14, July 7, 1998, of Proc. Natl. Acad. Sci. USA (95, 7939–7944), the authors wish to acknowledge an earlier paper that had escaped their attention. In an article entitled “Identification of RB18A, a 205 kDa new p53 regulatory protein which shares antigenic and functional properties with p53” [Drané, P., Barel, M., Balbo, M. & Frade, R. (1997) Oncogene 15, 3013–3024], Drané et al. report the identification of a human protein, RB18A, that interacts with several anti-p53 monoclonal antibodies, shows general DNA binding properties, and stimulates p53 binding to DNA. The cDNA-derived protein sequences of RB18A and TRAP220 are nearly identical, there being minor sequence variations and an extended N terminus on TRAP220. Apart from the effect of RB18A on p53 binding to DNA, the study of Drané et al. did not report any additional functions of RB18A and, in contrast to the findings with TRAP220, provided no indications of its presence within a larger multiprotein coactivator complex.