Answer-Find the missing letters. DGJ, FIL, (?), GLQ, INS, KPU.

There are two series DGJ, FIL, HKN and GLQ, INS, KPU. The first letter in every group of the series comes after a gap of one letter, i.e., D, F, H, and the second and third letters of each group have the same sequence, i.e., GIK and JLN. Same is the case with the second series.