  A four-dimensional dilaton-gravity action whose spherical reduction to two
dimensions leads to the Jackiw-Teitelboim theory is presented. A nonsingular
black hole solution of the theory is obtained and its physical interpretation
is discussed. The classical and semiclassical properties of the solution and of
its 2d counterpart are analysed. The 2d theory is also used to model the
evaporation process of the near-extremal 4d black hole. We describe in detail
the peculiarities of the black hole solutions, in particular the purely
topological nature of the Hawking radiation, in the context of the
Jackiw-Teitelboim theory.
