  We report finding kiloparsec-scale radio emissions aligned with parsec-scale
jet structures in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 1239 using the
Very Large Array and the Very Long Baseline Array. Thus, this radio-quiet NLS1
has a jet-producing central engine driven by essentially the same mechanism as
that of other radio-loud active galactic nuclei (AGNs). Most of the radio
luminosity is concentrated within 100 parsecs and overall radio morphology
looks edge-darkened; the estimated jet kinetic power is comparable to
Fanaroff--Riley Type I radio galaxies. The conversion from accretion to jet
power appears to be highly inefficient in this highly accreting low-mass black
hole system compared with that in a low-luminosity AGN with similar radio power
driven by a sub-Eddington, high-mass black hole. Thus, Mrk 1239 is a crucial
probe to the unexplored parameter spaces of central engines for a jet
formation.
