Ho-Hyung Woo, PhD

Laboratory of RNA-Protein Interactions

E-Mail Address: 
Short Bio: 

Dr. Woo received his PhD from the University of Minnesota, Twin Cities, and his undergraduate degree from the Korea University, Seoul, Korea. He did postdoctoral work at the Memorial Sloan-Kettering Cancer Center, New York.

His research goal is to understand the molecular mechanisms of RNA structurome formation. He is interested particularly in how RNA-Protein interaction determins the RNA secondary strucuture which regulates translation as well as deadenylation of mRNAs.

In translational reseach, he is interested in the molecular basis of metastasis in epithelial ovarian and breast cancers. Abnormal expression of proto-oncogenes c-fms and CSF-1 is an important prognostic factor. CSF-1 encodes colony stimulating factor-1 (CSF-1) and c-fms encodes receptor tyrosine kinase (CSF-1R), a sole receptor to CSF-1. His research focuses on post-transcriptional and translational regulation of c-fms and CSF-1 by means of RNA-Protein interactions and miRNAs.

Research Information
Summary of Research Activity: 
Repressor Loop Formation in Translation 
In post-transcriptional regulation of mRNAs, RNA binding proteins (RBP) are important trans-acting regulators. RBPs work either as activator or repressor of translation. We are particulary interested in repressor loop formation by RBPs during translation repression. RBP vigilin is a repressor for c-fms mRNA translation. We propose that vigilin is involved in the reperssor loop formation.
 
Our research indicates that both Vigilin and HuR work together to coordinate the translation of c-fms mRNA. Dysregulation of coordination between Vigilin and HuR can cause abnormal expression of c-fms mRNA.
 
 
Translation-7 copy.jpg
 
 
 
Deadenylation and Bulk Translation
Rate of translation is one of the critical factors, determining protein abundance in a cell. After a pioneer round of translation in which 80S ribosome scans the linear mRNA, a cap-dependent mRNP closed-loop is formed for bulk translation. However, detailed analysis about the transition from linear to closed-loop formation is yet to be studied.
 
Deadenylated mRNAs are generally thought as a translationally inactive form. However, our data shows that nucleolin-induced, deadenylated mRNAs are associated with heavy polyribosomes, indicating deadenylated mRNAs are in the translationally active state. In general, newly synthesized mRNAs are either assembled in a translation initiation complex or deadenylation-decay complex. In mRNA decay, deadenylation is the major step followed by decapping and exonuclease digestion.  However, mRNA deadenylation may have a previously unidentified function to enhance bulk translation.  After a pioneer round of translation, a mRNP closed-loop is formed by joining the 5’-cap and 3’-poly(A)n tail by RNA-binding proteins. Binding of PABPC to the poly(A)n tail and to the eIF4G in eIF4F complex results in a mRNP closed-loop for bulk translation. PABPC is also involved in the microRNA-directed mRNA decay by scaffolding deadenylation complex. Importantly, we documented that nucleolin interacts with the PABPC and works together for deadenylation and mRNP closed-loop formation; i.e., we observed that nucleolin enhances the microRNA-directed deadenylation of CSF-1 mRNA, but increases the translation of CSF-1 mRNA. Nucleolin interacts to the Pan2/Pan3 and CCR4-NOT deadenylation complex, indicating nucleolin’s involvement in the mRNA deadenylation. Nucleolin also interacts with the eIF4F translation initiation complex, suggesting another role of nucleolin in translation initiation. We found that an increased level of deadenylated mRNAs is associated with heavy polyribosomes in nucleolin overexpressed cell lines. Together these results indicate that nucleolin-mediated deadenylation is not followed by mRNA decay, but can lead to the bulk translation by forming poly(A)n-less mRNP closed-loop.  
 
We propose that a non-canonical mRNP closed-loop lacking poly(A)n tail can be formed by nucleolin for bulk translation. In this model, nucleolin enhances deadenylation of the mRNA and induces the formation of poly(A)n-less mRNP closed-loop by binding dsRNA formed between the mRNA 5’- and 3’-UTR complementary sequences. These complementary sequences are found in nucleolin-targeted mRNAs including CSF-1 and AKT1 mRNAs. Nucleolin is proposed as a mediator for the transition from the canonical to non-canonical poly(A)n-less mRNP closed-loop to enhance the bulk translation.
 
 
 

Translation copy.jpg

 

Selected Publications: 
 
2014:
Autocrine inhibition of the c-fms proto-oncogene reduces breast cancer metastasis assessed with in vivo dual-modality.
Experimental Biology and Medicine. 239: 404-413.
 
 
2013:
Nucleolin mediates microRNA-directed CSF-1 mRNA deadenylation, but increases translation of CSF-1 mRNA.
Molecular & Cellular Proteomics. 12: 1661-1677. (Cover paper)
 
Post-transcriptional regulation of proto-oncogene c-fms by RNA binding proteins in breast cancer.
Oncogene and Cancer. Chapter 13. pp295-316. 
 
 
2012:
Regulation of colony stimulating factor-1 expression and ovarian cancer cell behavior in vitro by miR-128 and miR-152.
Molecular Cancer. 11:58 doi:10.1186/1476-4598-11-58.
 
 
2011:
Post-transcriptional suppression of proto-oncogene c-fms expression by vigilin in breast cancer.
Molecular and Cellular Biology. 31: 215-225.
 

 

2010:
Inhibition of the c-fms proto-oncogene autocrine loop and tumor phenotype in glucocorticoid stimulated human breast carcinoma cells.
Breast Cancer Research and Treatment. 129: 411-419.
 
 
2009:
Regulation of non-AU-rich element containing c-fms proto-oncogene expression by HuR in breast cancer. 
Oncogene. 28: 1176-1186.
 
 

 

 

Professional Information
Professional Affiliations: 

 

Professional Society

  • American Society for Biochemistry and Molecular Biology
  • American Society for Microbiology

 

Journal Editor

  • AIMS Molecular Science
  • European Journal of Molecular Biology
  • Archives of Biomedical Sciences
  • VRI Cell Signaling
  • VRI Biological Medicinal Chemistry

 

Academic Information
Doctorate: 
University of Minnesota, Twin Cities
Undergraduate School: 
Korea University, Seoul, Korea