Identification of SAP155 as the target of GEX1A (Herboxidiene), an antitumor natural product.
GEX1A is a microbial product with antitumor activity. HeLa cells cultured with GEX1A accumulated p27(Kip) and its C-terminally truncated form p27*. GEX1A inhibited the pre-mRNA splicing of p27, producing p27* from the unspliced mRNA containing the first intron. p27* lacked the site required for E3 ligase-mediated proteolysis of p27, leading to its accumulation in GEX1A-treated cells. The accumulated p27* was able to bind to and inhibit the cyclin E-Cdk2 complex that causes E3 ligase-mediated degradation of p27, which probably triggers the accumulation of p27. By using a series of photoaffinity-labeling derivatives of GEX1A, we found that GEX1A targeted SAP155 protein, a subunit of SF3b responsible for pre-mRNA splicing. The linker length between the GEX1A pharmacophore and the photoreactive group was critical for detection of the GEX1A-binding protein. GEX1A serves as a novel splicing inhibitor that specifically impairs the SF3b function by binding to SAP155.
Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan.
Makoto
M
Hasegawa
Tatsuhiro
T
Miura
Kouji
K
Kuzuya
Ayu
A
Inoue
Se
S
Won Ki
Sueharu
S
Horinouchi
Tetsuo
T
Yoshida
Tatsuki
T
Kunoh
Koichi
K
Koseki
Koshiki
K
Mino
Ryuzo
R
Sasaki
Minoru
M
Yoshida
Tamio
T
Mizukami
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D001688:Biological Products / Q000737:chemistry / Q000494:pharmacology*; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D005233:Fatty Alcohols / Q000737:chemistry / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D015394:Molecular Structure; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D011714:Pyrans / Q000737:chemistry / Q000494:pharmacology*; D012322:RNA Precursors / Q000037:antagonists & inhibitors / Q000235:genetics; D012326:RNA Splicing / Q000187:drug effects / Q000235:genetics; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
D000970:Antineoplastic Agents; D001688:Biological Products; D005233:Fatty Alcohols; D010750:Phosphoproteins; D011714:Pyrans; D012322:RNA Precursors; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear; C112491:SF3B1 protein, human; C076087:herboxidiene; D050760:Cyclin-Dependent Kinase Inhibitor p27