BRCA2 and Smad3 synergize in regulation of gene transcription

Oncogene (2002) 21, 5660 5664 2002 Nature Publishing Group All rights reserved 0950 9232/02 $25.00www.nature.com/oncBRCA2 and Smad3 synergize in regulation of gene transcriptionOlena Preobrazhenska1,2, Mariya Yakymovych1,2, Takashi Kanamoto1,3, Ihor Yakymovych1,

Rostyslav Stoika2, Carl-Henrik Heldin1 and Serhiy Souchelnytskyi*,11Ludwig Institute for Cancer Research, Box 595, Husargatan, 3, SE-751 24, Uppsala, Sweden; 2Institute of Cell Biology of Acad.

of Sci. of Ukraine, Drahomanova str., 14/16, UA-79005, Lviv, Ukraine;3Department of Ophthalmology, Hiroshima UniversitySchool of Medicine, 1-2-3 Kasumi, Minani-ku, Hiroshima 734-8551, JapanSmad3 is an essential component in the intracellular

signaling of transforming growth factor-b (TGFb), which

is a potent inhibitor of tumor cell proliferation. BRCA2

is a tumor suppressor involved in early onset of breast,

ovarian and prostate cancer. Both Smad3 and BRCA2

possess transcription activation domains. Here, we show

that Smad3 and BRCA2 interact functionally and

physically. We found that BRCA2 forms a complex

with Smad3 in vitro and in vivo, and that both MH1 and

MH2 domains of Smad3 contribute to the interaction.

TGFb1 stimulates interaction of endogenous Smad3 and

BRCA2 in non-transfected cells. BRCA2 co-activates

Smad3-dependent transcriptional activation of luciferase

reporter and expression of plasminogen activator inhibitor-1 (PAI-1). Smad3 increases the transcriptional

activity of BRCA2 fused to the DNA-binding domain

(DBD) of Gal4, and reciprocally, BRCA2 co-activates

DBD-Gal4-Smad3. Thus, our results show that BRCA2

and Smad3 form a complex and synergize in regulation

of transcription.Oncogene (2002) 21, 5660 5664. doi:10.1038/sj.onc.

1205732Keywords: BRCA2; Smad3; transcriptionThe receptor-activated Smad3 and Smad2 are essential

components in the intracellular signaling of transforming growth factor-b (TGFb); phosphorylation of these

Smads by TGFb receptors is the triggering event which

induces their interaction with other proteins, nuclear

translocation and initiation of transcription of target

genes (Piek et al., 1999; de Caestecker et al., 2000;

Miyazono et al., 2000). Smad proteins are involved in

regulation of expression of genes controlling such

processes as cell cycle, apoptosis, extracellular matrix

formation and dierentiation. Smad inactivating mutations have been found in various human cancers;

disruption of Smad signaling results in resistance of

tumor cells to the growth inhibitory action of TGFb.Thus, TGFb-specific Smads can be considered as

tumor suppressors (de Caestecker et al., 2000;

Miyazono et al., 2000). As transcription factors, Smads

can bind to DNA directly, e.g. Smad3 binds to the

CAGA motif, or they can form complexes...