title: A C-terminal Myb extension domain defines a novel family of double-strand telomeric DNA-binding proteins in Arabidopsis.
abstract: Little is known about the protein composition of plant telomeres. We queried the Arabidopsis thaliana genome data base in search of genes with similarity to the human telomere proteins hTRF1 and hTRF2. hTRF1/hTRF2 are distinguished by the presence of a single Myb-like domain in their C terminus that is required for telomeric DNA binding in vitro. Twelve Arabidopsis genes fitting this criterion, dubbed TRF-like (TRFL), fell into two distinct gene families. Notably, TRFL family 1 possessed a highly conserved region C-terminal to the Myb domain called Myb-extension (Myb-ext) that is absent in TRFL family 2 and hTRF1/hTRF2. Immunoprecipitation experiments revealed that recombinant proteins from TRFL family 1, but not those from family 2, formed homodimers and heterodimers in vitro. DNA binding studies with isolated C-terminal fragments from TRFL family 1 proteins, but not family 2, showed specific binding to double-stranded plant telomeric DNA in vitro. Removal of the Myb-ext domain from TRFL1, a family 1 member, abolished DNA binding. However, when the Myb-ext domain was introduced into the corresponding region in TRFL3, a family 2 member, telomeric DNA binding was observed. Thus, Myb-ext is required for binding plant telomeric DNA and defines a novel class of proteins in Arabidopsis.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, USA.
authors.forename: Zemfira N
authors.initials: ZN
authors.lastname: Karamysheva
authors.forename: Yulia V
authors.initials: YV
authors.lastname: Surovtseva
authors.forename: Laurent
authors.initials: L
authors.lastname: Vespa
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Shakirov
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018744:DNA, Plant / Q000378:metabolism; D019281:Dimerization; D018745:Genome, Plant; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020598:Proto-Oncogene Proteins c-myb / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D035321:Telomeric Repeat Binding Protein 1 / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D020598:Proto-Oncogene Proteins c-myb; D034501:Telomere-Binding Proteins; D035321:Telomeric Repeat Binding Protein 1