Yh. Shen et al., DNA-BINDING DOMAIN AND SUBUNIT INTERACTIONS OF TRANSCRIPTION FACTOR-IIIC REVEALED BY DISSECTION WITH POLIOVIRUS 3C PROTEASE, Molecular and cellular biology, 16(8), 1996, pp. 4163-4171
Transcription factor IIIC (TFIIIC) is a general RNA polymerase III tra
nscription factor that binds the B-box internal promotor element of tR
NA genes and the complex of TFIIIA with a 5S rRNA gene. TFIIIC then di
rects the binding of TFIIIB to DNA upstream of the transcription start
site. TFIIIB in turn directs RNA polymerase III binding and initiatio
n. Human TFIIIC contains five different subunits. The 243-kDa alpha su
bunit can be specifically cross-linked to B-box DNA, but its sequence
does not reveal a known DNA binding domain. During poliovirus infectio
n, TFIIIC is cleaved and inactivated by the poliovirus-encoded 3C prot
ease (3Cpro). Here we analyzed the cleavage of TFIIIC subunits by 3Cpr
o in vitro and during poliovirus infection of HeLa cells. Analyses of
the DNA binding activities of the resulting subcomplexes indicated tha
t an N-terminal 83-kDa domain of the alpha subunit associates with the
beta subunit to generate the TFIIIC DNA binding domain. Cleavage with
3Cpro also generated an similar to 125-kDa C-terminal fragment of the
alpha subunit which remained associated with the gamma and epsilon su
bunits.