hnRNP G elicits tumor-suppressive activity in part by upregulating the expression of Txnip.
Heterogeneous nuclear ribonuclearproteins (hnRNPs) are nucleic acid-binding proteins and have critical roles in DNA repair, telomere regulation, and transcriptional gene regulation. Previously, we showed that hnRNP G has tumor-suppressive activity in human oral squamous cell carcinoma cells. Therefore, the identification of hnRNP G target genes is important for understanding the function of hnRNP G and its tumor-suppressive activity. In this study, we identify a known tumor suppressor gene, thioredoxin-interacting protein (Txnip) gene as a novel target of hnRNP G. Expression of Txnip is upregulated by wild-type (wt) hnRNP G but not by a suppression-defective mutant hnRNP G (K22R) in human squamous cell carcinoma. Wt hnRNP G binds and transactivates the Txnip promoter in vivo, whereas the K22R mutant does not. Furthermore, overexpression of Txnip alone in cancer cells leads to the inhibition of anchorage-independent growth and in vivo tumorigenicity in immunocompromised mice, suggesting a reversion of the transformation phenotype. These studies indicate that hnRNP G promotes the expression of Txnip and mediates its tumor-suppressive effect.
School of Dentistry, University of California, CHS 43-033, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA. kshin@dentistry.ucla.edu
Ki-Hyuk
KH
Shin
Reuben H
RH
Kim
Roy H
RH
Kim
Mo K
MK
Kang
No-Hee
NH
Park
D002352:Carrier Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011401:Promoter Regions, Genetic; D015533:Transcriptional Activation; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D002352:Carrier Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C510272:RBMX protein, human; C486715:TXNIP protein, human; D025521:Tumor Suppressor Proteins