title: Short repeats in the spa gene of Staphylococcus aureus are prone to nonsense mutations: stop codons can be found in strains isolated from patients with generalized infection.
abstract: Fifteen sequences with stop codons have been obtained in the course of standard methicillin-resistant Staphylococcus aureus (MRSA) spa typing. In nine of those sequences, stop codons occurred due to nonsense G-T and A-T transversions. G-T transversions would appear to be frequent in the spa gene, mostly due to symmetric mutational AT-pressure in the whole S. aureus genome and due to replication-associated mutational pressure characteristic of lagging strands of the "chromosome". A-T transversions would appear to be frequent in the spa gene mostly due to transcription-associated mutational pressure. Relative to other S. aureus genes, short repeats in spa are enriched by nonsense sites for G-T and A-T transversions; the probability of being nonsense for A-T transversion is high in that part of spa coding region. 13 out of 15 (87%) of the sequences with stop codons were obtained from strains isolated from patients with generalized S. aureus infection. Truncation of spa at its C-terminus is predicted to result in a protein that possesses functional IgG binding domains unable to be linked to the cell wall. This is discussed in light of the known fact that extracellular spa is a strong virulence factor involved in immune evasion.
authors.affiliation: Department of General Chemistry, Belarusian State Medical University, Dzerzinskogo 83, Minsk, Belarus.
authors.forename: Vladislav Victorovich
authors.initials: VV
authors.lastname: Khrustalev
authors.forename: Ehsanollah
authors.initials: E
authors.lastname: Ghaznavi-Rad
authors.forename: Vasanthakumari
authors.initials: V
authors.lastname: Neela
authors.forename: Mariana-Nor
authors.initials: MN
authors.lastname: Shamsudin
authors.forename: Alireza
authors.initials: A
authors.lastname: Amouzandeh-Nobaveh
authors.forename: Eugene Victorovich
authors.initials: EV
authors.lastname: Barkovsky
mesh_terms: D018389:Codon, Nonsense; D018388:Codon, Terminator; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics*; D059645:Mutation Rate; D012091:Repetitive Sequences, Nucleic Acid; D013205:Staphylococcal Protein A / Q000235:genetics*
chemical_list: D018389:Codon, Nonsense; D018388:Codon, Terminator; D013205:Staphylococcal Protein A
keywords: Mutational pressure; Preterminal codons; Truncation