  We demonstrate how to calculate perturbative components of the structure
functions F_1 (for unpolarized DIS) and g_1 (spin-dependent DIS) in
Double-Logarithmic Approximation, studying separately the cases of fixed and
running QCD coupling. We show that as long as only ladder graphs are accounted
for (throughout the talk we use the Feynman gauge for virtual gluons) there is
no difference at all between F_1 and g_1. However, accounting for contributions
of non-ladder graphs brings an essential difference between them. Applying the
Saddle-Point method to the obtained expressions for F_1 and g_1 allows us to
arrive at their small-x asymptotics. The both asymptotics are of the Regge kind
but with different intercepts. The intercept of F_1 proved to be greater than
unity, so it is a new contribution to Pomeron. Finally, we discuss the
applicability region of the Regge asymptotics and demonstrate that
inappropriate replacement of F_1 and g_1 by their asymptotics outside the
applicability region can lead to introducing phenomenological Pomerons for both
unploarized and spin-dependent processes.

High Energy Physics - Phenomenology;High Energy Physics - Experiment