title: A novel motif in geminivirus replication proteins interacts with the plant retinoblastoma-related protein.
abstract: The geminivirus replication factor AL1 interacts with the plant retinoblastoma-related protein (pRBR) to modulate host gene expression. The AL1 protein of tomato golden mosaic virus (TGMV) binds to pRBR through an 80-amino-acid region that contains two highly predicted alpha-helices designated 3 and 4. Earlier studies suggested that the helix 4 motif, whose amino acid sequence is strongly conserved across geminivirus replication proteins, plays a role in pRBR binding. We generated a series of alanine substitutions across helix 4 of TGMV AL1 and examined their impact on pRBR binding using yeast two-hybrid assays. These experiments showed that several helix 4 residues are essential for efficient pRBR binding, with a critical residue being a leucine at position 148 in the middle of the motif. Various amino acid substitutions at leucine-148 indicated that both structural and side chain components contribute to pRBR binding. The replication proteins of the geminiviruses tomato yellow leaf curl virus and cabbage leaf curl virus (CaLCuV) also bound to pRBR in yeast dihybrid assays. Mutation of the leucine residue in helix 4 of CaLCuV AL1 reduced binding. Together, these results suggest that helix 4 and the conserved leucine residue are part of a pRBR-binding interface in begomovirus replication proteins.
authors.affiliation: Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695-7622, USA.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Arguello-Astorga
authors.forename: Luisa
authors.initials: L
authors.lastname: Lopez-Ochoa
authors.forename: Ling-Jie
authors.initials: LJ
authors.lastname: Kong
authors.forename: Beverly M
authors.initials: BM
authors.lastname: Orozco
authors.forename: Sharon B
authors.initials: SB
authors.lastname: Settlage
authors.forename: Linda
authors.initials: L
authors.lastname: Hanley-Bowdoin
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017791:Geminiviridae / Q000378:metabolism / Q000472:pathogenicity*; D018551:Solanum lycopersicum / Q000821:virology; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000821:virology; D010940:Plant Proteins / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D014026:Nicotiana / Q000821:virology; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication
chemical_list: D004268:DNA-Binding Proteins; D010940:Plant Proteins; D016160:Retinoblastoma Protein; D014764:Viral Proteins; C080288:replication protein AL1, Begomovirus