Identification and characterization of a human smad3 splicing variant lacking part of the linker region.
Smad3 is one of the signal transducers that are activated in response to transforming growth factor-beta (TGF-beta). We have identified and characterized a splicing variant of smad3. The splicing variant (smad3-Delta3) lacks exon 3 resulting in a truncated linker region. We could detect mRNA expression of smad3-Delta3 in all investigated human tissues. Real-time PCR analyses demonstrated that the fraction of smad3-Delta3 mRNA compared to normal smad3 varies between tissues. The amount of spliced mRNA was estimated to represent 0.5-5% of the normal smad3 mRNA. When smad3-Delta3 is overexpressed in a fibrosarcoma cell line, the Smad3-Delta3 is translocated to the nucleus upon TGF-beta stimulation and binds the Smad responsive element. Using a CAGA luciferase reporter system, we demonstrate that Smad3-Delta3 has transcriptional activity and we conclude that Smad3-Delta3 possesses functional transactivating properties.
Section of Tumor Immunology, Department of Cell and Molecular Biology, Lund University, BMC I12, 221 84, Lund, Sweden. Christian.Kjellman@wblab.lu.se
Christian
C
Kjellman
Gabriella
G
Honeth
Sofia
S
Järnum
Magnus
M
Lindvall
Anna
A
Darabi
Ingar
I
Nilsson
Klaus
K
Edvardsen
Leif G
LG
Salford
Bengt
B
Widegren
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D020869:Gene Expression Profiling; D014644:Genetic Variation; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D008156:Luciferases