The formation of a large multiprotein-DNA complex that self-assembles on a tRNA gene through the sequential recruitment of the general initiation factors that compose the preinitiation complex (PIC), (which includes BDP1, BRF1, TBP, TFIIIC in human). The PIC engages RNA polymerase III on its DNA template strand and sparks polymerization of the first few RNA nucleotides.
RNA polymerase III type 1 promoter transcriptional preinitiation complex assembly