  AGN reverberate when the broad emission lines respond to changes of the
ionizing thermal continuum emission. Reverberation measurements have been
commonly used to estimate the size of the broad-line region (BLR) and the mass
of the central black hole. However, reverberation mapping studies have been
mostly performed on radio-quiet sources where the contribution of the jet can
be neglected. In radio-loud AGN, jets and outflows may affect substantially the
relation observed between the ionizing continuum and the line emission. To
investigate this relation, we have conducted a series of multiwavelength
studies of radio-loud AGN, combining optical spectral line monitoring with
regular VLBI observations. Our results suggest that at least a fraction of the
broad-line emitting material can be located in a sub-relativistic outflow
ionized by non-thermal continuum emission generated in the jet at large
distances (> 1pc) from the central engine of AGN. This finding may have a
strong impact on black hole mass estimates based on measured widths of the
broad emission lines and on the gamma-ray emission mechanisms.
