Nucleic Acids Research, 2002, Vol. 30, No. 20 4481-4488
© 2002 Oxford University Press
Identification of critical amino acid residues on human dihydrofolate reductase protein that mediate RNA recognition
Department of Medicine and Pharmacology, Yale Cancer Center, Yale University School of Medicine and VA Connecticut Healthcare System, New Haven, CT 06520, USA
*To whom correspondence should be addressed at VA Connecticut Healthcare System, Cancer Center, 111-D, 950 Campbell Avenue, West Haven, CT 06516, USA. Tel: +1 203 937 3421; Fax: +1 203 937 3803; Email: chueyale{at}yahoo.com
Previous studies have shown that human dihydrofolate reductase (DHFR) acts as an RNA-binding protein, in which it binds to its own mRNA and, in so doing, results in translational repression. In this study, we used RNA gel mobility shift and nitrocellulose filter-binding assays to further investigate the specificity of the interaction between human DHFR protein and human DHFR mRNA. Site-directed mutagenesis was used to identify the critical amino acid residues on DHFR protein required for RNA recognition. Human His-Tag DHFR protein specifically binds to human DHFR mRNA, while unrelated proteins including thymidylate synthase, p53 and glutathione-S-transferase were unable to form a ribonucleoprotein complex with DHFR mRNA. The Cys6 residue is essential for RNA recognition, as mutation at this amino acid with either an alanine (C6A) or serine (C6S) residue almost completely abrogated RNA-binding activity. Neither one of the cysteine mutant proteins was able to repress the in vitro translation of human DHFR mRNA. Mutations at amino acids Ile7, Arg28 and Phe34, significantly reduced RNA-binding activity. An RNA footprinting analysis identified three different RNA sequences, bound to DHFR protein, ranging in size from 16 to 45 nt, while a UV cross-linking analysis isolated an 
16 nt RNA sequence bound to DHFR. These studies begin to identify the critical amino acid residues on human DHFR that mediate RNA binding either through forming direct contact points with RNA or through maintaining the protein in an optimal structure that allows for the critical RNA-binding domain to be accessible.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  B. Song, Y. Wang, K. Kudo, E. J. Gavin, Y. Xi, and J. Ju miR-192 Regulates Dihydrofolate Reductase and Cellular Proliferation through the p53-microRNA Circuit Clin. Cancer Res., December 15, 2008; 14(24): 8080 - 8086. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. H. Elowe, J. E. Blanchard, J. D. Cechetto, and E. D. Brown Experimental Screening of Dihydrofolate Reductase Yields a "Test Set" of 50,000 Small Molecules for a Computational Data-Mining and Docking Competition J Biomol Screen, October 1, 2005; 10(7): 653 - 657. [Abstract] [PDF]
|
|
|
|
 |
|
 N. Skacel, L. G. Menon, P. J. Mishra, R. Peters, D. Banerjee, J. R. Bertino, and E. E. Abali Identification of Amino Acids Required for the Functional Up-regulation of Human Dihydrofolate Reductase Protein in Response to Antifolate Treatment J. Biol. Chem., June 17, 2005; 280(24): 22721 - 22731. [Abstract] [Full Text] [PDF]
|
|