Required for the cytoplasmic assembly and the nuclear import of RNA polymerase II. May facilitate the starting interaction between RNA polymerase II subunits RPB2 and RPB3 and the subsequent interaction of the resulting complex with subunit RPB1. May also participate in the transport of RNA polymerase II through the nuclear pore complex. Interacts with RNA polymerase II subunits RPB2 and RPB3. Interacts with the R2TP complex. Interacts with the nuclear pore complex subunits NUP100 and NUP116. Belongs to the Tango6 family. Truncated N-terminus.