  Recent angular-resolved photoemission experiments on LaNiO$_3$ reported a
renormalization of the Fermi velocity of $e_g$ quasiparticles, a kink in their
dispersion at $ -0.2$ eV and a large broadening and weakened dispersion of the
occupied $t_{2g}$ states. We show here that all these features result from
electronic correlations and are quantitatively reproduced by calculations
combining density-functional theory and dynamical mean-field theory. The
importance and general relevance of correlation effects in filled bands coupled
by inter-orbital interactions to a partially-filled band are pointed out.
