A Chlamydomonas protein that binds single-stranded G-strand telomere DNA.
We have identified a protein in Chlamydomonas reinhardtii cell extracts that specifically binds the single-stranded (ss) Chlamydomonas G-strand telomere sequence (TTTTAGGG)n. This protein, called G-strand binding protein (GBP), binds DNA with two or more ss TTTTAGGG repeats. A single polypeptide (M(r) 34 kDa) in Chlamydomonas extracts binds (TTTTAGGG)n, and a cDNA encoding this G-strand binding protein was identified by its expression of a G-strand binding activity. The cDNA (GBP1) sequence predicts a protein product (Gbp1p) that includes two domains with extensive homology to RNA recognition motifs (RRMs) and a region rich in glycine, alanine and arginine. Antibody raised against a peptide within Gbp1p reacted with both the 34 kDa polypeptide and bound G-strand DNA-protein complexes in gel retardation assays, indicating that GBP1 encodes GBP. Unlike vertebrate heteronuclear ribonucleoproteins, GBP does not bind the cognate telomere RNA sequence UUUUAGGG in gel retardation, North-Western or competition assays. Thus, GBP is a new type of candidate telomere binding protein that binds, in vitro, to ss G-strand telomere DNA, the primer for telomerase, and has domains that have homology to RNA binding domains in other proteins.
Petracek
M E
ME
Department of Plant Biology, University of Minnesota, St Paul 55108.
Konkel
L M
LM
Kable
M L
ML
Berman
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D016384:Consensus Sequence; D018076:DNA, Complementary; D016054:DNA, Protozoan / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019204:GTP-Binding Proteins; D017125:Genes, Protozoan / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins; D015800:Protozoan Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D016053:RNA, Protozoan / Q000032:analysis / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D016615:Telomere / Q000378:metabolism
D018076:DNA, Complementary; D016054:DNA, Protozoan; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C088955:GBP1 protein, Chlamydomonas; D010940:Plant Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D019204:GTP-Binding Proteins