Multiple mammalian proteasomal ATPases, but not proteasome itself, are associated with TATA-binding protein and a novel transcriptional activator, TIP120.
BACKGROUND
SUG1 belongs to proteasomal ATPase. Previous studies have demonstrated that SUG1 is associated with TBP. It is assumed to be involved in transcriptional regulation in addition to proteolysis. In this study, we investigated the association of mammalian SUG1 with TBP in more detail.


RESULTS
Pull-down experiments with TBP revealed multiple TBP-interacting proteins (TIPs) that were recovered dependent upon the presence of C-terminal conserved domain of TBP. By 2-D electrophoresis, we identified SUG1 in TIPs. By using far-Western analysis, we identified two proteins that could directly bind to TBP: SUG1 and another proteasomal ATPase (S4). Protein microsequencing and Western blotting identified all the remaining proteasomal ATPases (MSS1, TBP1, TBP7, and SUG2) in the TIP preparations. We present evidence that TBP and at least SUG1, MSS1, and S4 form a complex in the cell. However, no evidence of association of TBP with the 26S proteasome or its 19S regulatory unit was obtained. The molecular mass of the TBP/ATPases-complex, which also included a novel transcription regulatory factor, TIP120, was estimated to be approximately 800 kDa.


CONCLUSIONS
These results suggest that there is a novel multisubunit complex containing TBP and proteasomal ATPases. Based on our findings, we hypothesize that proteasomal ATPases are involved in transcriptional regulation in addition to proteolysis.
Makino
Y
Y
Department of Biology, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
Yoshida
T
T
Yogosawa
S
S
Tanaka
K
K
Muramatsu
M
M
Tamura
T A
TA
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D051381:Rats; D016385:TATA Box; D035181:TATA-Box Binding Protein; D014157:Transcription Factors / Q000378:metabolism*
C102896:Cand1 protein, rat; D004268:DNA-Binding Proteins; D009097:Multienzyme Complexes; D035181:TATA-Box Binding Protein; D014157:Transcription Factors; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases