title: The nucleocapsid protein of SARS coronavirus has a high binding affinity to the human cellular heterogeneous nuclear ribonucleoprotein A1.
abstract: The nucleocapsid (N) protein of SARS coronavirus (SARS_CoV) is a major structural component of virions, which appears to be a multifunctional protein involved in viral RNA replication and translation. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is related to the pre-mRNA splicing in the nucleus and translation regulation in the cytoplasm. In this report, based on the relevant biophysical and biochemical assays, the nucleocapsid protein of SARS_CoV (SARS_N) was discovered to exhibit high binding affinity to human hnRNP A1. GST pull-down results clearly demonstrated that SARS_N protein could directly and specifically bind to human hnRNP A1 in vitro. Yeast two-hybrid assays further indicated in vivo that such binding relates to the fragment (aa 161-210) of SARS_N and the Gly-rich domain (aa 203-320) of hnRNP A1. Moreover, kinetic analyses by surface plasmon resonance (SPR) technology revealed that SARS_N protein has a specific binding affinity against human hnRNP A1 with K(D) at 0.35 +/- 0.02 microM (k(on) = 5.83 +/- 0.42 x 10(3) M(-1)s(-1) and k(off) = 2.06 +/- 0.12 x 10(-3)s(-1)). It is suggested that both SARS_N and hnRNP A1 proteins are possibly within the SARS_CoV replication/transcription complex and SARS_N/human hnRNP A1 interaction might function in the regulation of SARS_CoV RNA synthesis. In addition, the determined results showed that SARS_N protein has only one binding domain for interacting with human hnRNP A1, which is different from the mouse hepatitis virus (MHV) binding case where the nucleocapsid protein of MHV (MHV_N) was found to have two binding domains involved in the MHV_N/hnRNP A1 interaction, thereby suggesting that SARS_N protein might carry out a different binding mode to bind to human hnRNP A1 for its further function performance in comparison with MHV_N.
authors.affiliation: Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, China.
authors.forename: Haibin
authors.initials: H
authors.lastname: Luo
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Kaixian
authors.initials: K
authors.lastname: Chen
authors.forename: Xu
authors.initials: X
authors.lastname: Shen
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
mesh_terms: D002999:Clone Cells; D004591:Electrophoresis, Polyacrylamide Gel; D005982:Glutathione Transferase / Q000378:metabolism; D005998:Glycine / Q000737:chemistry; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D019590:Nucleocapsid Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism; D045169:Severe Acute Respiratory Syndrome / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D014170:Transformation, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; C000619657:Hnrnpa1 protein, mouse; D019590:Nucleocapsid Proteins; D010446:Peptide Fragments; D012367:RNA, Viral; D011994:Recombinant Proteins; C000619656:hnRNPA1 protein, human; D005982:Glutathione Transferase; D005998:Glycine